Yes that is the expected outcome on the majority of games and you should keep it on for them, with MSFS 2020 it’s different, the architecture benefits from multithreading up to a certain point past that point it starts to hurt your performance. I don’t know the exact details to tell you why MSFS 2020 is like that because it’s not open source but I believe it has a lot to do with the fact that it is a simulator where certain things are not as easy to distribute in multithread as it normally would be for other games.
If you are overclocking your processor it would not hurt to try disabling it for a quick test, see for your self, it may vary from system to system, but from what I have tested with my old 9900K and my new 10900K HT disabled makes the game gain 5 to 8 FPS across the board.