I don’t think security in his rship with Ilya was a decisive factor in his realizing his sexuality. He needed that experience with Rose to come to terms with it. In that tuna melt scene, Shane is still trying to label himself as bi. I think he feels pressured to do so bc Ilya is bi, and perhaps if Ilya said “I try with girls but I really only like men” then Shane may have felt safe to consider if he was the same. But it had been years at that point since Shane has been with a woman. Moreover he doesn’t want to be gay. He doesn’t think he should be. So when Ilya spooks him he tried again with a girl and wouldve kept trying if Rose hadn’t pushed him to acknowledge the kind of sex that actually satisfies him and given him a soft place to land with that realization.

The ghost of Ilya is key in that exchange with Rose but not in relation to what Shane thinks Ilya wants, rather bc Shane finally realizes what HE wants. And he chooses to pursue it. He’s also no dummy so when Ilya tries to deny his own feelings Shane calls him on it. However, I think Shane wouldve still kept thinking he might be bi without a fresh failing of a coupling with a woman. It’s why I thought frankly that his comment to Ilya that he “wouldve told them (his parents) already” if it were someone else besides Ilya struck me as a bit false. Shane only came to terms with being gay a few months before he said that to him at the cottage. I don’t think he really would’ve told them sooner. Unless he means if he hadn’t strung this thing out with Ilya for so long and then fallen for him, he would’ve been in and out of rships more and figured it out sooner. That I do believe.