It's not as bad if you have one child or if there is a larger age gap between two children.
Or you have school age children.
But for us, we couldn't leave a big gap because, tbh, I'm no spring chicken (37 and this one, our third, will definitely be our last).
It's when you've got one in a buggy and then carrying the other in the sling that it starts to bite if you're third or fourth floor.
Or one has to be lead by the hand and the other carried.
And you have some shopping or stuff. Or you had a csection or assisted delivery and not a lot of family/friends to help out.
For us, the issue of outdoor space got to be too great and became a bit of a dealbreaker. Some people are okay with just going to the park, but tbh it's a real bonus to be able to work in the kitchen, leave the back door open and the kids and their friends can play out in the back, to BBQ, grow a bit of fruit/veg, have a picnic or a small party, stuff like that.
I think the fabric of the city has changed quite a bit, too.
My ILs were both brought up in tenements. BUT, back then, it was very common for children to play in the street unsupervised and not come to any harm. And in parks as well, even at fairly young ages. And in the communal gardens of tenements. This is not so now and sometimes, teh communal garden is no longer communal but owned by those on the ground floor or main door flats.
For us, we found the lack of garden space more and more restrictive as the children grew.
Also, care must be taken with regard to schools, unfortunately, particularly catchments for secondary schools. These can also increase resale value on a flat large enough to fit a family.
Before we left Edinburgh, we lived in The Shore area, which we really liked. There were a number of double uppers, but I'm not sure when they were converted. The ones in the converted houses it's pretty obvious, but tenement ones I'm not too sure about.
Hopefully someone will come along who has done it, but it might be worth contacting the council to see if that policy about the roof rings true.