This is definetly a statement, and i find it impossible to believe the devs are manipulating matches. How would they even do that?
This stuff could happen in ANY BF title, hell it can happen in probably every shooter. Cause people can leave, and others can join. If you have a match where you're ahead, and a bunch of players on the other team leaves, those empty slots will be filled by either bad, good or sweaty players. That's been a fact for YEARS now.
What do you think will happen if some players leave a match and those empty slots are taken by absolute units? There's now a higher chance that the game will turn. Maybe your team got complacent after that 300p lead, hell, maybe your team just wasn't that good to begin with.
This is in the end, just a game. If you're not having fun, there's no shame in just quitting the game for a couple hours.