I think rounds played is based on spawns, the more you die the more rounds you 'play' due to respawning. If you don't die, you just get healed so you're essentially playing the same round. So if you've got 35 rounds played and 30 deaths, it means you've survived 5 of the 35 rounds played, which is something which deaths don't really show, so it could be a good choke indicator to see how often you're actually surviving rounds. I could be wrong though, but there's a large correlation between deaths and rounds played, which is probably because of what I wrote above. Getting a lot of kills is great, but if you're dying in the process even though your team are still winning rounds, then maybe you're not solid enough.
I quite like it tbh