Now that you mention an actual relationship I agree with you. There were so many factors that wouldn't have made it work which is why I think whatever there was between them has long been over.
I did mention the word relationship in my initial post in the Shoma thread, not just now.
While I hold different views on the narrative, it was interesting to read your take on this "love-story in Russia". That detailed interpretation of "Je te veux" was new to me, so thank you for that!
Onto my own views, I think Tatsuki and Dai bonded over their shared disappointment with their results in Sochi and Dai was probably flattered by Tatsuki's obvious infatuation (I would love to know what Tatsuki told Dai when he couldn't "escape" in that room.

) He was also incredibly emotionally drained, which might've made him even more responsive to the attention from his kohai. Of course I might be wrong, but I just don't believe that this developed into more than maybe a pretty short-lived crush from Dai's side. (I'm not doubting Tatsuki's "more profound intentions" - sorry for the lack of a better expression.)
Regarding Dai's behaviour around Tatsuki in Sochi, we also have to take the cultural differences into account as it appears that among the younger generations even straight japanese close male friends are more touchy-feely with each other than western guys, at least when there's drinking involved which there most likely was before the closing ceremony. And yes, Dai appears to be like that with several of his friends in social situations - the giggling, touching, embracing, everything. (I don't know how close he is with each of them, but I can't imagine, that he has an increased romantic interest in all of them. But then again, who knows?

)
I also can't imagine Dai being so tactless to openly talk about wanting a partner right in front of Tatsuki at the Kansai honor ceremony had there indeed been more than a platonic, friendly bond between them at some point.
And aw, did Tatsuki tear up during that speech at his farewell ceremony?

Did it say so in the accompanying article? I can't judge from the picture and unfortunately there was no video material of it (I think).
It's a really interesting topic, but also almost entirely speculative.
On a completely different note: Do we know what Tatsuki is up to right now? Does he intend to do a doctorate/is he already working on one?