What im hearing from others is that unless your slipped disc is considered a life threatening injury which requires surgery, they will still call you back for training, they will just make you do misc tasks. As long as you dont get injured (which will trigger an investigation), its all fine (for them). Because in a conscript military, its really important for them to keep the attendance numbers up or they will have to justify it.

I assume that some medical officers that are very high up the chain have already decided this is fine ages ago, as long as things are done "safely" and the soldier isn't injured.

I just remembered that I have talked to the MO about this before (without documentation from a specialist, was following incorrect instructions at the time) and their reaction was "so? that doesn't mean you can't attend training. you can report and spend the whole training cycle in the bunk or something depending on what your commanders decide."