Open- or closed-cell insulation floor slab lateral

We have received the list of individual services from our slab company. As builders, we now have to decide between two options for the lateral insulation of the slab. However, I do not find these options clear; they rather confuse me. Here is the text from the company's letter:
"The builder was explicitly informed that the insulation protruding above the ground (air area) must have a plasterable surface. This means that a closed-cell waffle board (which may not extend even 5 cm below the ground—only usable above ground) should be installed or an open-cell white insulation should be applied. This in turn means that this material can only be installed as an open-cell insulation board.
The closed-cell waffle board is not an option because the exact boundary between the air area and new soil cannot be precisely determined.
Therefore, a high-quality closed-cell board without a plasterable surface will also be used above the soil area. This means that before plastering the insulation surface (above soil), the insulation must be roughened by hand with BHS.
Disadvantage: According to regulations, the plasterer would have the right to raise concerns and declare that he assumes no liability for the plaster."
I do not understand why "a closed-cell waffle board is not an option," but at the same time it is written that "above the soil a high-quality closed-cell board should be used," with the disadvantage that the plasterer may raise concerns???
I am at a loss!!! Maybe a knowledgeable expert can help me understand this and give me advice!
Many thanks in advance!