I didn't even want kids at 30! My "biological clock" (😝) kicked in around 32, met my DP around 36, had DC1 at 38 and DC2 at 40.
So no, I would Never assume!
I would also add, if you want to have a child, IMO you need to deliberately set about trying to make it happen. I haven't read your other thread, Op, so don't know if you're with a partner but if not first step is to get out there and find one, obviously! Join clubs, get sociable, put yourself out there. Make it clear on dates what you have in mind for your future so you're both clear. Biological factors aside there is no reason why at 30 you wouldn't have 12-15 years left to find a suitable partner and start a family, but the initial deciding factor is YOU taking charge.
I know a woman in her early-mid 40s who is grieving her lack of children and the life she'll never have as she'd "never fallen in love", but when I asked her why she never even considered partnering with an amenable man more for the shared purpose of having a family she was aghast... Couldn't even conceive of the idea (scuse the pun) so that was that. 🤷♀️
Life doesn't always happen in the idealised way we might have imagined in our teens/twenties but it's almost always salvageable!