Fundamenterder V4A - What is mandatory?

Hello house-building colleagues,

the following question: At the performance adjustment at the end of the planning phase, the construction company offers me the "fundamenterder in V4A instead of standard."

Now my question: Can they charge an extra fee for this?
Is the aforementioned quality grade not mandatory in construction by now (DIN 18014)?

In the construction description it says:
"A foundation grounding made of galvanized strip steel according to VDE regulation is installed in the foundation slab. In the basic calculation, we assume a soil characteristic stiffness modulus >= 15 MN/m2 and a maximum topsoil of 20 cm as well as a frost apron depth of 80 cm."
Background: Already in the offer phase, we commissioned the black tank according to which is now also being built (DIN 18533 W2.1-E).

Many thanks & best regards from Stuttgart.

Foundation earth electrodes lie in the concrete on the steel reinforcement of the base slab, galvanized steel is perfectly fine there. With a white or black tank this is not possible. The grounding around the house must then go into the soil. Therefore, V4A is required. This is called ring grounding.