Not true. It's been problematic in many games over the years. It doesn't generally cause frame rate issues as much as inducing stuttering or flat in out crashing the game or preventing it from running. It's the Norton Antivirus of the copy protection world.
It's very much a game-by-game thing. In some games it has barely any effect at all, while in others it's far more noticeable. Seems to come down to how well optimized a game is already and how the developers implement the checks.