I believe it is implied that it is per 100 plays used by the player. So, if you see a player with 12% TOR, that's per 100 plays used by that player, not per 100 team plays.
They use the same formula for teams. And it is TOV%, not turnover rate. For individual players turnover rate makes more sense, because that incorporates assists, while TOV% does not. It makes no sense to include assists on a team basis, because those plays are already accounted for with the FGA.
Poldi now suggest that it is better to use possessions instead of plays. Meaning, we are subtracting ORB from the team data.
TOV% = 100*TOV/(FGA+0.44*FTA+TOV-ORB)
Seems not like a bad idea.