Because in the countries occupied by the Nazis, they really did start interfering with style names. They weren't happy with German-derived names being used for Dutch beer. In particular, Dortmunder.
XVII. USE OF THE NAME "DORTMUNDER".
Mr Stikker says that the Ausfuhrgemeinschaft requires the Phoenix brewery to stop using the name "Dortmunder". The Phoenix brewery has asked the C.B.K. to take up this matter with the Ausfuhrgemeinschaft.
The C.B.K. has, however, advised the Phoenix to send to the Ausfuhrgemeinschaft a copy of the judgment concerning the procedure, which was won in 1928 on this matter. The C.B.K. thought it desirable not to come to the fore in this matter at this time.
The board agrees with this state of affairs.
Minutes of the management of the CBK on 10th December 1940, held at the Amsterdam City Archives, document number 31121-1, pages 287-288.
Basically, the CBK (the Dutch brewers' organisation) wanted to keep its head down. Probably not a bad idea given the nutcases they had to deal with.
Intermediate beer was something between Lagerbier and heavy beer strength. At this point, 8.8º to 9.1º Plato.
XXIII. DISPENSATION CONCERNING THE CASE DORTUUNDER,
Mr. Ivens says that four breweries have applied for the above-mentioned dispensation for beer in the intermediate category. In view of the possibility of action against German beer names, it is desirable to reserve the name Dortmunder for beer of a higher quality.
Mr. Smits van Waesberghe sees the merits of this, but nevertheless points to the commercial objections that arise from this for the breweries concerned.
After some discussion, the board decides that the dispensation for the name Dortmunder for intermediate beer will only be granted to those breweries that until now regularly sold such beer under that name, which dispensation will expire on July 1, 1941.
Minutes of the management of the CBK on 21st January 1941, held at the Amsterdamse Stadsarchief, document number 31121-1, page 271.
OK to call your beer Dortmunder, then, but only for a few more months. That's very generous of the occupiers.
In Belgium, it went even further, banning even more style names.
"Mr Stikker says that it has recently been forbidden in Belgium to give a Belgian beer names that indicate a foreign origin, such as "Pilsen", "Baviere", "Munich", "Dortmund"."
Minutes of the management of the CBK on 14th November 1940, held at the Amsterdamse Stadsarchief, document number 31121-1, page 297.
Didn't they have more important things to worry about than beer names? Like that war they were busy losing.