Oh, that makes sense then - the CPU has only 4 cores and then this feature is disabled. The feature disables the first core because the first core is also used by a lot of other processes. This may cause stutters. But it is only enabled when the CPU has at a minimum of 6 or more cores. The reason for that is simple: if you have 4 and you drop one then 3 may not be sufficient to run the game smoothly at all.
In your case, the warning is meaningless in my opinion 🙂 .