Yes...it is. Although, after watching the balance of red/green on the teams, I'm pretty sure that the matchmaker pays attention to the player "skills," possibly more than say, ohh, the nine Type 59's, or the 6 TD's it just put on one team (and none on the other).
I'm also quite certain that within a few percent, the win/loss ratio means nothing. I'd say 90%+ of players have win ratios of 48%-52%. I still like seeing it though. It gives you something to look at when that jackass in the scout (you all know him) blazes to the enemy base before anybody is ready, AND there are no arty, I look at his loss ratio, and it's usually 45% or less. Or that KV-5 sitting in our base telling everybody that he's a bad-ass sniper. Yep, he's a 45% player too.
Also, when I get put on the team facing a platoon on the other side with all purple names, I know what we're in for...