Yeah, kinda, CUDA is c++ that I can't run cppcheck or clang tidy on, and the important bits are either calls into the cu* libraries which are c style, or kernels, which are really their own thing.
Yes, kernel code is GPU style rather than CPU style.
But the CPU-drivers of CUDA are all C++. Albeit a C-like API (cudaMalloc, lol), but its a clang compiler for the CPU code nonetheless. If you have complex GPU + CPU interactions, you'll need to be a C++ expert.
Even if you aren't doing GPU work and sticking "only" with CPU-side CUDA, its all C++.
I imagine some work is also useful on CPUs, and C++ is one of the most efficient languages.