Dry floor truss roof boarding

Hello,
I ordered a dry floor truss instead of a studio truss for our bungalow under construction for an extra charge of almost €3000. This is, of course, to be able to use the floor for storage purposes. The seller of the general contractor, as well as the project planner, advised that once the roof frame is in place, i.e., before the roof is covered, the corresponding OSB boards or tongue-and-groove boards should be stored in the roof structure with a crane to cover the attic floor. This way, the floor can be boarded later on accordingly. The opinion was also that later on, the small attic hatch would not allow any building materials to be brought up to the attic.
Today I spoke to the construction manager about this. He reacted very dismissively, saying this is not possible, the drywall contractor would always have to move the boards or wood away when installing the insulation on the roof. And I should contact the drywall contractor and ask him what he thinks about it. Why I should do this is not clear to me. Of course, he has no interest in moving the boards back and forth. But I do not see this as our problem. You cannot sell something that later is not usable. Besides, it was communicated differently in the consultation with the project planner.
When I asked how we could then board the floor and use it, he said one could pass the tongue-and-groove boards piece by piece up through the attic hatch after the house is completed. (The floor area is over 130 sqm.)

How have other builders solved the problem of boarding the floor?
Thank you.

Since your house is otherwise secret here, we lack a spatial understanding of the connections. As is also the case with the processes: where is a drywall installer (presumably building the interior walls of the unknown upper floor of the unknown house) involved when the crane operator (from the drywall installer's perspective actually pretty much above the clouds) lets some floorboards float over the still uncovered roof frame?

You can't sell something that is later unusable. Besides, it was communicated differently during the consultation with the project planner....

Here theory and practice differ again. In your consultations, you bought things that are probably difficult to implement in practice. Even if it sounds easy on paper...

Here theory and practice differ again.

I would put it this way: only the signed word applies.

However you decide to do it. (I know both approaches). Bringing the boards/shiplap onto the attic before completion. As well as afterwards through the hatch, certainly more complicated but doable.

You have to come to an agreement with the craftsmen. Especially if it is a [GÜ] or similar arrangements, and I agree with the predecessors that the written word counts. If you suddenly want things that are not part of the agreement, you are on thin ice.

So, once again more precisely. It is a bungalow with a wooden beam ceiling. The boards /Rauspund that may have been previously lifted into the roof truss would hinder the drywall installer when installing the insulation in the attic into the wooden beam layer/that is, the ceiling of the masonry. Furthermore, according to the construction manager, and I find this the most absurd thing, there would be no space for the sealing anyway, because the insulation is about 4 cm higher than the beams..., so it practically protrudes from the beams and the sealing which I consider necessary would "squeeze" the insulation.