Would you be willing to answer a few brief questions about PlayStation Forums?
Last match I completed had 6 downed and 6 revives on the game summary screen. The website correctly shows 6 revives, but lists only 1 for knockdowns.
It also showed 1 suicide, which I did not do during the game. I had one death and it was from a knockdown with teammates subsequently going down or getting choked.
Knockdowns in general do not seem to match the in-game stats for co-op games.