TL;DR: Nnew accounts spawn less minions on wave 2 then lvl10+ish accounts.

I got to know this by creating a new account that I'm gonna be using to play with my little nephew. Made another one to confirm and had the same result. Here is a the vid showcase:

I think this should be moderated too. To have it either all accounts must be lvl10 or above or something like that maybe?