Correct, and its a problem often overlooked or people dont know about it.
Basically what has happend is that FreeSync and GSync exist as a solution to a problem that shouldn't exist in the first place. Game developers aren't given enough time to optimize the games, are too lazy, or GPU drivers are involved as well.
A console game at 30 FPS optimized would run smoother than an unoptimized game at 60 FPS.