I don't think it's stupid that the uke thinks it's gonna be over if he confesses.
Because in the past when he directly asked the seme if he would like a boyfriend, the seme literally said, "Hm? Nah. It would be pretty annoying, don't you think? It would feel like I'm shackled or something. Well, overall I just don't feel like it anyway. I don't need that kind of thing."
Just based on this alone it's perfectly reasonable for him to assume the seme is not interested in a relationship at all. Furthermore, the seme says that for physical stuff, a fuck buddy works just fine. And he also says that he thinks it's pretty weird when his customers start confessing to him that they love him.
So, even if you say that the uke is not longer a customer, and some time has passed. They never had conversation about dating and relationships and love, since they met again. So, how is the uke supposed to know that the seme's perspective has changed after a breakup and he now wants something serious?
Also, the seme was being persistent about asking him to confess because he was jealous and he also likes the uke. But how is the uke supposed to know his intentions behind asking such things?
In conclusion, I think it's reasonable for the uke to behave the way he did. It's not silly to be that protective over his feelings. He just likes the seme so much and doesn't want to lose him. So, it's a natural course of action to fight so hard to not give in and confess.
It think that rather than being afraid he'll get hurt if he confesses, he's more concerned that the seme will stop even having sex. The seme disappeared from his life once, and perhaps he would like to avoid that more than anything. But that's just my perspective. (=・ω・=)
Also, I dun think it's cowardice to want to protect yourself & avoid getting hurt. It's just human. (●'◡'●)
"The seme is being persistant beecause he is jealous.....how is the uke supposed to know"
Well because it is obvious that the seme is jealous / he WANTED the uke to admit he likes him.
So i do think its stupid that despite that, the uke doesnt even consider that the seme might have a different mindsit about relationship. But the uke is 100% still believing the seme is the saem as in the past.

For once the uke is right. Even if the seme is getting mad (which seems to imply he likes the uke), he himself still has the mindset that dating is just a bother.
But I do think its stupid that the uke thinks it's gonna be over if he confess, even though the seme was asking for it.