Sometimes. And sometimes the core engine may be in C++ but the game logic is in C# (Unity). There are plenty of games whose performance demands are not so high

Sometimes. And sometimes the core engine may be in C++ but the game logic is in C# (Unity). There are plenty of games whose performance demands are not so high, that a GC language can work fine. There are also many examples of realtime 3d games, that used garbage collection, and were extremely successful (minecraft, subnautica). These were high quality games, though both do suffer from performance downsides, related at least indirectly to using GC languages.