The architect is right. I wasn’t sure – I work in NRW – but a look at the Bavarian administrative service website brought clarity:
Required Documents
[*]current excerpt from the cadastral register
[*]site plan, unless it concerns changes to building structures where exterior walls and roofs as well as the use are not altered
and further documents
In the so-called preliminary site plan, all heights and sewer lines are drawn, which are needed to determine the placement of the new building on the property as well as its connection to public utilities.
Once for the surveying of the property when purchasing it and 4 times for the house construction.
Edit: the surveyor is needed a total of 4 times; sorry, I phrased that ambiguously.
Rhenish regards