It doesn't make any sense from a physics perspective that tracking range is inferior to reliable detection range. STT = lots of energy and frequent returns on a specific target.
I also doubt that any fighter fire control radars will ever stop the pilot from _attempting_ a track/lock on a detected target. It would be, tactically, immensely disadvantageous.
Also, the fire control radar doesn't know everything. The pilot may have radio information/visual on a contact and may want to attempt a lock because they know the radar should be able to pick it up despite not having a scan echo yet.
I'm very sceptical that fighter fire control radars won't allow the pilot to attempt a lock in _any_ point in space, despite not having a detected target. A detected return should not be a requirement for an _attempt_ to lock/track. Any such limitations would put the pilot at tactical disadvantage in many situations such as brief notches, where the pilot _knows_ the target is still there, and wants to force locking attempts in that volume of space.