#*right

so here's the quote in question (which i'm sure you know, but for everyone else):

Interviewer: Let me ask you about one of your new songs, ‘This One’. About a marriage? Paul: A relationship, yeah. Interviewer: And about not expressing emotions and feelings.  Paul: You get those moments where you always think; "I’m saving it up. I’ll tell him one day." And you know what happens. A lot of people, John for instance, getting back to that subject. He died. Um.. I was lucky. The last few we- months that he was alive we’d managed to get our relationship back on track. We were talking, having real good conversations. Real, nice and friendly. George, actually, didn’t get get his relationship right. I think they were arguing ‘till the end, which I’m sure is a source of great sadness to him. And I’m sure in the feeling of this song that George was always planning to tell John he loved him, but time ran out. That’s what the song’s about. Like, there could never be a better moment than this one. Y’ know now. Take this moment to say… "I love you."

(source) (again, an archived blog, but it's audio so i'm using it as a legit source)

argument for it being about john

well, to start with, paul immediately answers with "i'll tell him one day" which, regardless of if it's about john, is a very blatantly queer answer. maybe a slip of the tongue, who knows, but there's not much question at the least that this song is romantic. so paul saying it's about a "him" is very interesting, even if it's not john. (edit: given the youtube video linked below, it can also be heard as "them". i still don't hear "them" or think it's continuous, but that is one interpretation & hearing of this interview and it's a valid one!)

second, he does connect it to george and john's relationship, but he does it in a way that's just again connecting the song to him and john. he says "i'm sure in the feeling of this song that george (...etc)" which is just him saying he thinks george can relate to the feeling of the song.

and ofc back to the beginning of the quote, right after saying "i'll tell him one day" he says "a lot of people, john for instance (...)" which is just connecting that sentence to john. he goes on to say they got their relationship right, but then at the end loops back around to saying the song is about regretting not saying "i love you", which we know from "here today" and other paul quotes he does deeply regret not saying to john. so an Entire Song about that regret is not like. unfeasible to be about john.

i will say, i at least think this song is about more than one thing. he says here it's about that type of relationship he had with john (or the nebulous "him" who i mean. who else would that be? tara?) and then he does also talk about how he had fun w the storytelling w the word play on "this swan" and the hindu imagery. (edit: also with the full context of the youtube video below, this is even more relevant, because paul also talks about family and a "her". imo, it's more than likely a song about many people/relationships. some people think that one of those is john, myself included!)

argument for it not being about john

like you said, it is a bit of a rambling answer! and saying it's about john IS just an interpretation. paul saying "him" could've been a slip of the tongue, or maybe he had some other romantic relationship with a man we're not privy to, or maybe he did completely mean all those lines platonically and it's about various men he's been friends with or even john in a platonic way.

he does also connect the song to george and john, so it could be about that. i've also seen someone posit that here he is trying to reach out to george in his own way- thinking george must have the same regrets as him with john & thus this is his attempt to repair that relationship before they have those regrets with each other too.

and ofc, it could just be a totally hypothetical song. he never says it's about his own life, and he does include a lot of fictional imagery about a swan in this song. he could just be telling a story he doesn't necessarily relate to.