The uke's just human

The thought about marriage can be scary for some people. If I were an omega, meeting my "mate", a man I don't know and who says that he wants to marry me, I would have run away fast too. Because accepting a partner brings changes, and whats important here, it limits your personal freedom/space espacially for an omega. The fear of bonding is nothing unnatural. Could the uke be nicer? Yes. But remember, people react different to fear. At first, the uke didn't noticed that he hurt the seme, and as he realised, he couldn't face him because of guilt. That's not a good, but often a common reaction, if it's about uncertainty and fear.
I feel also sorry for the seme. He was just too enthusiastic and scared the uke away. It's hard to fall in love with someone, that doesn't want to bond. It's a toxic combination of longing (seme) and emotional self-protection (uke).