Does the builder want a bitumen coating on the finished plastered base?

Hi, yes you're right. So it was filled with Z0 soil and then just a layer of gravel/crushed stone. But according to the site manager, that wouldn't have been necessary either.

Ok, then one should possibly also ensure the drainage of the [Spritzschutzstreifen]. Not that later water stands in it and damages the base plaster.

The rest is filled up with topsoil. A drainage system is actually not planned. According to the earthworks contractor, the soil is very permeable to water. So what type of bitumen do I need now? And if you leave 20-30cm space to the base? Should this area just be backfilled with sand and gravel or similar on top?

At the gravel drip, the dimpled membrane is placed between the base plaster and the gravel. With the dimples facing the plaster, this also provides minimal ventilation and allows drying.

So I would do it or we did it like this:
Bitumen thick coating up to ground level
Dimpled membrane in front
For the splash protection strip (and you definitely need it, otherwise the plaster will be totally dirty after a few months):
Concrete curbstones at 30-50 cm distance from the wall (without a boundary, lawn and gravel will mix sooner or later)
If necessary, install drainage if the ground is not permeable
Fill with gravel/crushed stone