I know how it is in theory and how it was starting from ver 15.
Earlier, I usually was setting 8 cores and 2 tasks; because in earlier versions 4 cores were giving out optimal performance. Anyway, during initial solution, before the sweep, only one task is used (no domain distribution).
As you see above, I had serious problems with CPU load distribution, where only 2 cores of 8 were loaded, and other 6 were idle almost all the time, except results copy/fetch phase, where OS distributes many small disk IO operations.
The day we upgraded to Premium, I finally got a uniform full load for all the CPU cores, and the corresponding performance.
So I have a natural suspicion that you updated DrivenModal solver operates differently under different types of license, regardless of available HPCs number.