I’m not sure why you strip women of their agency in this situation? Surely if a woman wants children and her partner doesn’t/isn’t sure/can’t commit to a suitable timeframe then it is up to her (and not solely down to her partner) to decide whether that desire for children is more important than to her then her current partner/relationship? Why is it his responsibility to “let” her focus on something that is totally up to her? He may well be happy with the relationship as it is, but if she isn’t then surely it’s on her to end it and move on?
I’m obviously not talking about situations where the man says “not now, but definitely next year” or similar but just keeps putting it off- that is unfair, they should be honest about their intentions and if they really don’t want children/children with this woman then they should be clear about it. It is cruel to lead a partner on about something as fundamental as having a family. But equally, the woman needs to be clear about it too- if she wants children more than her relationship with this particular man, then it’s up to her to act on that and end the relationship to seek a partner who does want the same things.
I find it odd that some women feel the need to lay all the blame for these situations at the feet of the male partner- obviously those who lie or deliberately mislead their partners are at fault but I think it is often the case that both parties haven’t been entirely honest with each other. Or they are but one party doesn’t have the courage of their convictions and chooses to stay, but unhappily. Some men definitely need to be more upfront, but so do some women- some of whom also need to be prepared to make control of their own lives rather than sit back waiting for this issue to fix itself.
Yes, a man lying about wanting children to a partner who definitely does want them is cruel, but being clear he isn’t sure if he does want children or not isn’t “stringing” anyone along, it is quite probably the truth.
Obviously, if he really means “never” or “not with you”, then he should be honest about that- but I don’t think we can know for sure which is the case here.
OP- if you want children more than you want a relationship with this man, then you should end it and move on. If he isn’t sure, he isn’t sure and he isn’t wrong/cruel to feel that way- but if you are sure it something which is non-negotiable for you, then you need to take responsibility for your life and act accordingly.