Perhaps there has been some misunderstanding of what is being asked due to language differences.
The back cavity is of the same dimensions. It is indeed the stud or screw mounting and openings that is the main difference between the tremolo routings rather than the back cavity.
If you ordered the Tremolo Back cavity only and drilled for the studs etc yourself that is an option. Or Floyd with an angled pocket, or Schaller Floyd recessed but with that you would end up with a recess for where the fine tuners would go and you might not want that.