I had a radius plate fitted about 5 years back just before XMAS. I was back at work in january but on light duties, as my work at that time involved regular lifting of 1-10kg objects. I did twinge it a bit when I dropped a stack of paperwork and tried to catch it.
To be honest, what they’ve asked you to do does seem quite reasonable – if mentoring someone is possible without any practical demonstrations.
Looking at from their point of view, they’ve paid you for 6 weeks already (for effectively a self inflicted injury) and made a sensible request that takes your limited ability into account. You’ve refused. Do not be surprised to find that your work boots bear a faint whiff of the boss’ urine upon your return to work 😉 Of course, if you are regularly treated like dirt then they’ve only got themselves to blame…