That works...
As a certified old bastard, I have heard more complaints about disabling, horrible pain forcing guys to go home early than most doctors have. My favorite was a guy almost 20 years younger than I am tell me he didn't show up to work because he hadn't shit in almost an entire day.
Luckily, I'm a sentimental, caring kind of guy, so before firing him I asked him if anybody was asking him to shit out of a tree. At the time, I was just running a crew for a friend until he could hire some new people, and he hired the guy back a few days later, but put him on another crew. Within a week he was doing his no-show act, again. This time, because his mother was dying. The boss realized that he had given him time off the previous year to attend his mother's funeral, and fired him on the spot.
I suspect that attitude has a lot more to do with whether you can climb a tree than any physical limitations (other than the obvious ones, like being in a wheelchair or not having arms).