No, I’m afraid it isn’t.
It’s a notebook graphics solution. The iMacs are not big enough to fit a desktop graphics card. So Apple uses notebook hardware, which is smaller and produces less heat, but also offers much less performance than its desktop counterparts.
It’s five years old. So, it may have been a high-end chip in 2012, but not according to today’s standards.
Unfortunately I was not able to play your screencast - I’m on Windows/Linux machines and have yet to find a video player that can handle that SCC file.
But make sure to experiment with the VSync settings in the nvidia driver: Is it off, then turn it on. Is it on, try turning it off. Without seeing the effect, I’d still say this sounds like a tearing/screen refresh issue. Changing the “Window Draw Method” in Blender’s user preferences might also help.