Certainly for me, we are running a Microsoft Product that specifies a minimum CPU of 2.66GHZ.
We have a D v3 series which lists a couple of different CPU's. One of these is too low at 2.49. Another is even lower at 2.1 and the other is fine at 2.8GHZ
But due to not being able to select the CPU that would meet the requirements, we now have to pick a different, more expensive Dds v5 Series just in order to pick something that ONLY specifies a CPU that meets the requirement.
Even more, whilst these CPU's say they will boost to meet the requirements, Microsoft have confirmed back that it is the core clock that needs to meet the minimum requirement to remain under support.