Seems common on most battery and Dynamo Taillights I have particularly the European ones..
mine, A B&M 4D Toplight only came with the rack because the whole bike was built up by the Koga Miyata Company.
if you just buy a rack, it will not be included.

I have Busch and Muller Toplight taillights , on my Tubus Rack [2 horizontal holes 5cm apart]
the batery Cateye lights are also fine.. my TL 500 screwed on the usuual 2 vertical hole 2cm apart, brackets..

some others pop off to not be Nicked. clip says on.. people zip tye those on to not be road debris..