Can't comment on the back order, but it does seem oddly long to wait.
My son in law has a JD zero turn, I think Z950 ? It has mulch on demand. It mows really pretty, and I thought maybe I should have a mulcher. Turns out, for 60d deck it's not "on demand" meaning you put the mulch kit on, and there's no switching on / off.
I try to mow when it's dry, and not too long. But stuff happens - sometimes I mow wet, long, leaves etc, and I think (at least for me) trying to mulch during these times would be a problem.
So I never bought the kit. Sometimes I wind up raking a bit, but I'm ok with that