Usually can have a spread of meanings, from "almost always the case" to "just over half the time", but that doesn't mean that when it is used, you can pick the definition that best fits your argument, and declare that to be the proper meaning for that instance. Context clues matter. So, what are the context clues for what "usually" means in this case? The context is that if he wasn't summoned by a goddess, it would be extremely suspicious because of how uncommon it is, and that he has to immediately try to deceive her, or else it could expose them. If "usually" meant "50.1% of the time" this wouldn't be a big deal to cover up, because it wouldn't be strange. Thus we can see that "usually" in this case means "almost all the time" but she can't say it "always" happens, because he wasn't summoned that way, so maybe there have been other, extremely rare cases as well.
In reality, though, your attempt at semantics about what "usually" means is to distract from the reality that he was not summoned by a goddess. You even reword it for your own purposes of "meet with a goddess and remember it", even though that isn't what the manga says. Felice is saying that his summoning was unusual because he wasn't summoned by a goddess at all. There are multiple quotes from the manga that directly state he WAS summoned by Felice and that he WASN'T summoned by a goddess. For it to be a "refutation" (according to your definition) it requires "lack of evidence" , but since the manga has multiple statements, by Kyouya and Felice that he wasn't summoned by a goddess, that means there is evidence to support that claim.
For you to claim that a goddess might have been involved, despite a lack of manga statements saying they were, and in spite of manga statements saying they weren't, means you are the one using conjecture. Since I pointed our your lack of evidence, and showed both evidence and logical reasoning for rejecting the idea that he was summoned by the goddesses, that means I was the one doing the "refutation" according to your definition. Rather than a "concrete refutation for lack of evidence" you are offering a "shaky conjecture" that the evidence that is provided might be later contradicted by something down the line.
As for the "beings called goddesses" statement, that is more likely to mean that Kyouya is throwing shade at them. He sees Felice as good, so if they are against Felice, then he rejects them as being "goddesses" because he sees them as evil. Regardless, it is another red herring by you, because even if we say that "goddesses and other powerful beings, like Felice, that could also be called goddesses are capable of granting powers" most of what we know about special powers and roots comes from Kyouya, and he is the one that still says he doesn't have a special ability. Even with the drug, he is saying that there has to be a powerful entity granting a special ability through the drug. The exposition we are given here about how "Special abilities" are granted is given by Kyouya. The same Kyouya who has told us, in multiple chapters (6 and 17, at least) that he doesn't have a "Special ability". So to pick and choose when he is a credible source, based on whether his statements might help or hurt your argument is insincere, at best.
There is evidence that he does not have a unique ability. There are direct statements to that effect in multiple chapters. There is evidence that he was summoned by Felice. There are direct statements to that effect in multiple chapters. There is evidence that he was not summoned by goddesses. There are direct statements to that effect in multiple chapters. There is no evidence that he does have a unique ability, that he was not summon by Felice, or that goddesses were involved in his summoning. There IS evidence that he could gain a unique ability.
Thus, in terms of which side is using evidence, and which side is using conjecture, you are the one relying on conjecture. I am just refuting your statements based on your lack of evidence. You said I was "building up a bubble", but I am the one that is using direct quotes from the manga, and specific chapter references, while you are just saying, "Nuh uh, because I said so." You are not arguing from the manga, but just that there are still chapters to be written and that those may later contradict what is currently written.
Is it possible that the author will later change things? Yes. Does that mean taking the author at his word right now is "merely conjecture not based on evidence"? No. There is evidence, and plenty of it. I've also offered multiple context clues that show that, based on how much they hate Felice and fear her, that if they were involved in him going there, they would have been keeping a close eye on him and that world, to further support what the manga directly says.
To put it another way, somebody is saying, "Silver-backed Chevrotains have been found to still exist" and showing pictures and eyewitness testimony, and you are saying "the pictures might be fake, even though I don't have a way to prove they are fake, and the eyewitnesses are probably lying, possibly being paid to lie. It is conjecture to believe Silver-backed Chevrotains aren't still extinct, and merely refutation to say there isn't any evidence they still exist because the evidence being presented MIGHT be fake evidence."
