Not on something this fundamental, and after so long no.
With him 30 and her 27. Especially if the GF wants to have children. Why would she? He made his feelings clear, she was 'silly' for trying to discuss it and her wants for the future. He was the big I am and would make the decisions unilaterally so she could just sit down, be quiet and wait for the day if and when he decided that he wanted to discuss it.
This guy had lived in the GFs house and had all the benefits of a marriage, but when asked about a discussion on the future possibility of getting married he belittled and demeaned her. He could see she was upset and didn't address it, or offer any further discussion.
As others have said, it's fine if he's not ready or will never be ready to marry, but he doesn't get to shut down discussion about it. That's not how loving relationships work, you're supposed to communicate honestly with each other.
He's lucky he got three months grace while she processed all this and dealt quietly with her hurt. He's even luckier after that shoddy treatment of her, that she was going to let him stay in her property till after Christmas but he shot himself in the foot by harassing her.
I think there's more to this than OP is letting on, or possibly it would be kinder to say that there more to this than the OP actually knows.
There's little hints that the son is actually a bit of an arsehole frankly. Future faking and possible cocklodging #1, Son's attitude over the possibility of marriage discussion #2, then the co-dependant 'shut up' panic ring #3, the harassment to take him back #4, and then the planned ambush after she asked him to leave because of the harassment #5.
I think we'd hear a very different story if the GF were able to tell her side. I think she's suffered the death of this relationship through a thousand cuts. I think she's been very smart, and I wish more young women knew their worth and had such iron self esteem as she did.
I think the OP's son has treated his exGF very badly, cruelly in fact. I don't think he's the catch he or his mum thinks he is 😂