I’m starting to make it a habit to check my warzone stats after each match, and I noticed that regular wins and losses would change to win/ loss count, win percentage and total warzone matches you played.
I noticed however Join In Progress matches if they lead a loss, it doesn’t count as a match at all so the loss tally doesn’t go up for one, and the total warzone games doesn’t change.
Best way to see this is to look at win/ loss for past 20 games on Halo waypoint.
They change for me in the game because I check after the game. Haven’t really checked WP though.