The situation I often saw was 16-20 players ~ half would be CA-BB-CV. The host would insist on waiting for 24 even if it took several minutes during quiet hours. We'd get a few DDs and everyone would be happy.
So I posed this question to this host as well as others when they claim 24 ~ an extreme example ~ Would a room with 16 CA-BB-CV generally result in more experience than a room with 24+ only FF/DD? According to at least one host - yes - because we have at least 24 players.
The 24 claim is too simplistic. I don't play blitz for XP but if I had to I'd look at the following factors: General balance: try to avoid the 3BB/3CV with 1BB/1CV total. With a limited number of ships if there are some CA/BB/CV - playing > waiting. I can understand holding out if it's only FF/DD. Personally I also like to keep ship count lower to avoid a luck based torp-fest.
I would also like to ask Servatis if they found some sort of test/documentation regarding the 24 blitz or was it based on usual speculation that goes on in blitz mostly amongst players that have barely any experience/knowledge about the game? Last week the topic de jour was reload stat for torpers....