There have been so many Unity games which do not manage to throttle GPU usage. Battletech was another one where at the menu it would keep the GPU at 100%.
Not sure why devs allow this, but with Battletech it was a known issue that was never fully resolved.
You'll have to enable v-sync to limit framerate. I enable it always (or fps limit) because I don't like blasting my GPU at 100% which makes it hot and loud.
Not sure why devs allow this, but with Battletech it was a known issue that was never fully resolved.