You are helping - they clearly need the additional training, and you’re doing everything you can to supply that. Their job can’t be relying on you.
They shouldn’t (and almost certainly don’t) have delegation authority.
For corporate bingo, the keywords are upskill, cross-training, and bus factor.
As others have mentioned, it refers to the gear shift. But it actually has a meaningful origin - many years ago, the gear order was not agreed upon. Many cars had a gear shift that was PNDLR (which I’ve heard pronounced “pendler”), where reverse was at the end. At the time, it was useful to tell the difference between a PRNDL and a PNDLR shift.
Of course that was all before 1971, when PRNDL was mandated by the US government.