Sorry, but in the FAA world that is exactly what it means.
IF the runway has a 2.5nm MRS, then the min wake is 2.5nm, IF the runway has a 3nm MRS, then the min wake is 3nm. I just went through this at KMEM and FedEx.
The FAA defines min separation as just that, a minimum, measured from threshold to the FAF, or in the case of RECAT, 10nm
Here are the details from FAA RECAT matrix. This is also what is built into ATPA.
and the example...
note minimum 2.5nm sep...