There is only 1 definition of a thread. A thread is a piece of code that is executed on a processor, and which contains the state of a processor and its registers ( where in memory it was executing, memory locations, stack, state of the function it was executing,... ). Which thread gets executed is for the operating system to decide depending on several things ( priority or affinity as its called in windows , type of thread, what layer of the os requests time etc etc ).

Source : https://en.wikipedia.org/wiki/Thread_(computing)

There is , at its core, no such thing as a "cpu thread". This is marketting speak to indicate how much threads a cpu can processes at the same time. Depending on the operating system's scheduler, the processor and the type of instruction it needs to process, a cpu could processes 16 threads at the same time on a 8 core/16thread cpu so its constantly using everything of a cpu. However, if 2 or more threads are doing similar instructions it is possible a thread has to wait for the other to process despite them not having anything to do with each other. Thats on the processor's scheduler to decide btw.

Source : https://en.wikipedia.org/wiki/Hyper-threading

Adding more threads to the os' thread queue isnt magically going to make things faster. Take a look at dolphin's thread and core usage. They have ( used to?) be against adding more threads to the emulator because it made 0 sense to do so, despite some games running slow. This resulted in dolphin at one point using 2 cores 100% on a quad core cpu, while 2 were doing nothing. Just because adding threads that would 90% of the time do nothing was a waste of resources and processing time.

Source : https://forums.dolphin-emu.org/Thread-multi-thread-explanation

I have a feeling you dont understand how this stuff works, as you have given me nothing of proof, details or anything of how any of this works. Have you profiled the game? Checked gpu busy vs cpu busy? Looked beyond the cpu % usage? Checked on different hardware?