You are 100% correct but you also read harem isekai mangas. How curious that you are singling out this one in particular for logic.
I have fun calling out any and all manga for the stupid stuff in it. It's entertainment in and of itself.
There are a lot of manga out there with dubious logic. Though if a manga takes a turn into frustrating territory, that sort of entertainment drifts away from just casual poking snarky fun to serious complaints.
For now, this one is fairly box standard with what it's offering and is still fun, but I knew what we were getting into based on the tags/title/premise. As with any manga, from the get go it's either you find actual unexpected gold or a story that's got some issues but is still entertaining or a frustrating mess. I wouldn't call this gold, but it's also not a heaping pile of unreadable trash. It stands firmly in the middle but we're also very early in the story.
If ever it takes a turn and actually is serious about it's world building, internal consistency, power structure and systems, all while still committed to the main goal of the story without horribly or unexpectedly deviating away in an unsatisfactory manner, then my assessment and opinion will alter just the same.
Otherwise, I'm currently treating it the same as I do other thinly veiled wish fulfillment fantasy story.
I'll enjoy the trashy story. But I'm also gonna have fun poking at the trashy story.
I hope that makes sense to you.