The whole point is, Vivado should calculate the divider values (and provide the corresponding macros for this) based on the configured clocking.
The embedded developer simply might not know how the clocking is configured and maybe even cannot define the macros correctly.
Also while I haven’t tested this explicitely, I don’t think it would have worked with 1Gbit on my end without writing the SCLR since I have the device conneted to an interface that is capable of 1Gbit, but I might have had the 100Mbit/s config in FreeRTOS in the way there, so I’m not sure.