In the web novels the loner part makes even less sense because he's banged all of them already. Officially the whole loner thing is that he can't form or join parties but as we've seen you can team up with people without officially forming a party.
so in short the loner part of the title is just the mangaka daning in the backround while you got jebaited plays.
Well, you can also include the part of MC always doing everything by himself without the help of almost anyone, to the point that his body brokedown. Aka., Suffering in Solitude.
The "Loner Life" in the Title is a bit of a misassumption I guess, since "ひとりぼっち (Hitori Bocchi)" can also mean "aloneness/loneliness/solitude".
I mean, since start of the series, MC has done everything by himself not allowing his classmates to dirty their hands, like MC had even killed people to protect them.
And just to add, just because someone is surrounded by people, doesn't mean they aren't feeling loneliness, because of what they have to do or can't do.
Aka., you might bang hundreds of women, but still be alone as there might not be someone who is equal or of same wavelength as you.
I mean, if you remove the Dungeon Emperor Girls, who actually try to help MC on equal terms. The rest of the girls are basically useless by themselves and heavily depend on MC for everything and give almost nothing in return (especially in Manga & Anime).
Though I haven't yet read the WN or LN, I think that if those three Dungeon girls didn't join MC's side, none of his girl classmates would have slept with MC even in the WN (might be wrong as haven't read it yet).
