Drempel yes/no, which height

Hello everyone,
I have another question burning on my mind. We are currently having a semi-detached house built through the developer. In the attic, there is currently a knee wall with a 50cm rough construction dimension as standard. The roof itself rests on the floor. So no knee wall, if I understood correctly. But somehow, that’s neither here nor there. The drywall installer has now offered to move the knee wall forward to 1m. Cost point 280 euros net for just under 6 meters. He also somehow needs to know everything promptly, for whatever reason.
I thought that would come after underfloor heating and screed. Or how does that work? What is behind the wall then? The floor without screed? That would be quite dirty in terms of storage space.
Isn’t it more practical to leave out the knee wall completely and do it yourself later? I imagine the floor covering etc. all a bit “cleaner” that way. But then the roof would meet the floor at a sharp angle. That would raise the question of appearance.
Maybe you have a few tips for me. What makes sense, what is worthwhile?
Thanks to you all

In the attic, there is currently a standard knee wall with a raw construction dimension of 50 cm. The roof itself rests on the floor. So no knee wall, if I understood that correctly.

You should really turn your assumptions into researched facts. Since you are asking here without any pictures and I couldn't find the house in question in your thread history, I can unfortunately only answer "42," which is probably unsatisfactory though ;-)

What do you mean by “42”?
Kniestock is definitely not present. The roof rests on the ground and has a slope of 33 degrees. Do you need to know anything else?

That depends on how the DG is used. General answers and recommendations cannot be given.

The attic is used as a hobby room / guest room.

A small door will definitely add to the cost of the knee wall if there is to be storage space behind it. We postponed the problem until later, since we have enough storage space in the basement. Acquaintances of ours store things there like extra roof tiles, tiles to replace broken ones, and skis. For stuff that you will rarely need, it is a good storage space.