Roof terrace - pedestal support - standing water

Hello,
I would like to hear your opinion.
We have a roof terrace in the new building.
The substrate is concrete. Then I am not sure what comes next, definitely also an insulation layer, but all of this is under a sealed membrane (not sure what material this membrane is made of). Openings for rainwater drainage are present. There is also a slight slope.
On this membrane, slabs were laid using pedestals. Under each pedestal is a piece of mat (similar to those base mats for training equipment), then a stone slab, and on this stone slab another piece of mat. On top of this, the actual tiles were laid continuously.
Today I removed two of these tiles to take a look at how it looks there. It rained heavily the last two days, but not today. What was noticeable and strange to me was that there was quite a lot of standing water visible, which drains slowly or not at all.
Is standing water problematic? Could it freeze in the worst case or damage the membrane?
Or is this completely normal and harmless?
The construction management said in summer before handing over the house that this is not a problem, the water would evaporate and having some water standing is completely unproblematic for the material.
One of these mats visible as the substrate was even floating in the standing water....
Is this maybe all just defective and still to be reported as a defect (if still possible at all)?
Thank you

If there is a slope and drainage, the water should drain away. Do you mean that with openings? As long as the building protection mats are only point-based, the drainage should not be obstructed. I would say that the slope is not appropriate.

Was there water there after rain before the terrace was built as well? I would not want it like that.

Exactly, the openings refer to the drainage.
The whole thing was planned in such a way that there are 2 drains, each at the corners.
The mats are only laid pointwise.
Before the whole thing was laid, some water already remained.
I questioned this several times. Then, as I said, the statement came that it would all evaporate. Since it was midsummer, it actually evaporated quickly again and again. Now it has also rained heavily for days.
I attached some pictures from the summer...
Thank you.
Do you see this as a defect?

The water does seem to flow towards the drain. But could it be that the drain hole is positioned slightly too high? And that it either should have been placed more in the corner or the slope from the corner should have been more towards the drain hole?

Possible, but I cannot judge? How do you assess the situation? Could this become a problem or is it simply just poorly regulated? Or a defect?