There was this ROCm bug I was watching for awhile: https://github.com/ROCm/ROCm/issues/5706 - This is about the GPU clock remaining at max frequency, but that can drive the fan speed to increase.

It doesn't happen with Vulkan backends, so that is what I have been using for my two dual R9700 hosts.

EDIT: The bug is closed but there were mentions of the issue still occurring after closure, so who knows if it is really fixed yet.