I don't think it's anything like that. I think Taehan is just still in shock with the whole Doyun could be pregnant situation. Do remember, this all happens like in a day, him finding out he knotted Doyun, going to the hospital to get tested, & getting the results. I think he feels really guilty that when he was in his rut he knotted Doyun.
I think Taehan just needs some time to process everything. And it looks like Doyun brought up marriage (in a teasing way) to attempt at cheering him up because he was in a shocked state, not really saying anything. And I do noticed that when Taehan does say 'Marriage' in the next panel of him it seemed like his eyes widened a bit, It had looked like some sort of realization clicked at that moment for him.
I'm thinking too they haven't even said 'I love you' to each other yet. And I'm not counting when Taehan said it in his rut b/c he doesn't even remember what he did or said when in his rut. I would like a 'I love you' face to face while either of them are not in their heat or rut. I can imagine Taehan saying 'I love you' and Doyun being like 'I know' (b/c Taehan said so when in his rut). Haha! All we can do though is speculate. But either way the next season english version will be coming back next month, so not too much longer to wait to see what happens next.
So what? Season 2 just ended with that vague 'marriage'? Does seme didn't want to marry or smthng?