[2021] Match making again

So, the matchmaker actually does look at what you're describing, however it only sees Nation and Class.

There was no "swap because the Smolensks are Russian Cruisers, and Stalingrad are Russian Cruisers. Had it been two Des Moines instead of Stalingrads, then one of the Des Moines would have been swapped with a Smolensk. This would provide 1 Russian Cruiser on each team, and 1 US Cruiser on one side and 2 US Cruisers on the other.

This process is described in the How It Works: Matchmaker video:

Video Direct Link: https://www.youtube.com/watch?v=r7PmOMVLgsE