I dont think it has anything to do with modern dating. People like this existed 30 and 50 years ago.

He wants to keep his options open because he isn’t sure you are “the one” but he isn’t interested in denying himself pleasures of sex.

I personally recommend not to sleep with people until you two are more serious about each other. Jusf few days ago you weren’t even sure if he is the right guy for you but now you are already intimate. Jusf few days ago you said he doesn’t even ask you any questions about you: major RED flag indicating lack of interest yet you ignored red flag and slept with him.

Why if you aren’t sure and neither is he? And if you don’t want just casual sex then why sleep with someone you have big reservations about?