But is Jinwoo really committing suicide EVERY loop though ? Is he never killed by someone else or due to outside circumstances ? IMHO the loop only resetting when it's suicide would be a major plot hole and highly unrealistic.
The Hounds have already been very suspicious to straight up antagonistic towards Jinwoo in this past loop. I have a hard time believing there never has been a loop they managed to off him in some way. It's more likely the loop restarts with Jinwoo's death in general, at least that would make more sense.

The time loop as we know now starts with, Jinwoo's suicide and how the title resonates with the greek legend of sisyphus.
I feel the suicide being the part of the story kind of resonates with Albert Camus's book "The myth of sisyphus" where he argues that instead of escaping through suicide one must accept the absurdity of life and rebel against it to be truly free from it. And as his book ended with sisyphus learning his fate, I think the loop will end with Guwon realizing his.
"I leave Sisyphus at the foot of the mountain! One always finds one's burden again. But Sisyphus teaches the higher fidelity that negates the gods and raises rocks. He too concludes that all is well. This universe henceforth without a master seems to him neither sterile nor futile. Each atom of that stone, each mineral flake of that night filled mountain, in itself forms a world. The struggle itself toward the heights is enough to fill a man's heart. One must imagine Sisyphus happy."