" thought that PDP-11 assembler was called "C". Surely it should be possible to train the engineers needed to maintain the code."
nope. it's called 'MACRO' but the C language has many features that are actually implemented by PDP-11 in hardware.
Register modes include 'pre' and 'post' auto-increment and auto-decrement, and a sensible method of index-based indirection. Some of these are (obviously) found in other processors too (like x86, M68K) but PDP-11 pioneered a lot of this by implementing it in the hardware like that. The intent was to avoid accumulator-based operations by using GP registers, and significantly reduce the size of the code.
Anyway, it was pretty good tech at the time. If it weren't for the 16-bit limited address space (and klunky ways of extending it beyond 64k), it might have become the basis for PCs.
conclusion: what you said is _almost_ correct. The 'C' language WAS developed for PDP-11 and VAX (as part of developing UNIX, well known history), and has PDP-11-isms in it like '++' . It's like 1 step above MACRO assembler on a PDP-11.
(I'd give examples but I might get some detail wrong and get down-voted over it, ha ha ha)