Notice those are all (except arguably CUDA) very mainstream languages. All four of AMDs are niche. Upstreaming this into pytorch would double the number of languages used. (Although HIP is very similar to CUDA)
There is absolutely nothing out of the ordinary here. Yes, it's multiple languages, but not any more or any different than what you'd use on an Nvidia platform (except obviously for the assembly part -- AMD's ISA is different from PTX, but that's to be expected).
It's having both Triton and HIP in the same project which I find weird. It feels very fragmented to me to use two high level languages. Maybe it makes sense given Triton is easier to use but less fully featured, but it definitely didn't strike me as normal.
I would be interested to know if NVIDIA use more than CUDA and PTX/SASS to write CUDNN and CUBLAS.