I believe Centaurus is correct.
AFAIK it was introduced by GFS after the over-the-runway collision in which poor Holly Smith died.
It was not used during tower hours, but when the zone was MBZ (as it was then). Was intended to inform/warn pilots, particularly in darkness, if another pilot thought he was the same as you in the sequence.
Can't recall any mid-airs during non-Tower hours since, so maybe it is fulfilling its purpose ?