While I can see their point in the reasoning for it (UK has a smaller playerbase) I agree and still think its BS. UK is known for its navy, its our thing.
Playerbase means little.
They were the significant naval power throughout the time period which the game covers and most players will understand to some degree the significance in which the Royal Navy. Most people could name the Hood, the Kelly, the Prince of Wales, Exeter, Ajax and Achilles. You could counter that with Bismark and Tirpitz but the allies greatly outnumbered the axis
The potential number of people that would purchase RN ships, in my personal opinion, would outstrip that of the German or Russian navies and the likely revenue would be greater especially as Germany's on-water navy wasn't a significant factor in the latter parts of the war and the Russians were quite far behind the other powers in naval warfare.
I couldn't even name a Russian ship or class of ship from any era.
Disclaimer: I am British, from England specifically, and I am biased but I do think that it's poor PR and the incorrect decision from a business point of view.