There's more than that. Not a huge amount more but still.

- multiple large companies contribute to each of the larger AoT compiler projects; think AMD's contributions to LLVM and GCC, and multiple have their own internal team for handling compiler work based on some OSS upstream (eg Apple clang)

- various companies have their own DSLs, eg meta's Hack, the python spinoff Goldman has going on, etc.

- DBs have query language engineers which are effectively compiler roles

- (most significantly) most hardware companies and accelerators need people to write toolchains; Triton, Pytorch, JAX, NVCC, etc. all have a lot of people working on them