Accurate delay compensation is necessary to enable redundancy. IF you need multiple GrandMasters at different locations in the facility, using independent RFoF systems and antennas, they will have different GNSS delays, and that difference will propagate down into uncertainty on the hosts. There are other ways to eliminate this uncertainty than to characterize the full delay, but if the racks are on opposite ends of a giant data centre, that might be as or more difficult than just going through those motions.
If you just have one GM, then sure, the delay means you will have a larger fixed offset from TAI/UTC, but that won't be consequential, and you'll still get the benefits of a tightly synchronized monotonic clock. Until that GM fails, and it all goes haywire.
It's a hard problem to solve. You end up doing something like the NIST TMAS service (see https://www.nist.gov/programs-projects/time-measurement-and-...) using differential common view measurements to create a "Multi-Source Common-View Disciplined Clock".
If you just have one GM, then sure, the delay means you will have a larger fixed offset from TAI/UTC, but that won't be consequential, and you'll still get the benefits of a tightly synchronized monotonic clock. Until that GM fails, and it all goes haywire.