This is actually very untrue, if every player blocked 1-200 other players the permutations of possible group combinations is massively restricted and the amount of computation required to make those matches goes up significantly. Without actually doing the math, its admittedly a bit complicated, I would estimate even 25 blocked players would have a noticeable effect on matchmaking speed as well as a significant load increase to matchmaking servers. There is probably already a noticeable increase in computation load on their servers with even 2 blocked players.