Do you have a link to where you heard this?
What makes sense to me is that the application to animate the screen is simply an application. Settings in the app will determine the time interval of the animations. The CPU simply runs the app, so it shouldn't care what the app is set up to do. The speed of the animations are way slower than the clock speed of the CPU, so I don't think the CPU would suffer even if the setting is at 0. I would think it would actually have to work harder to slow things down. Games run fast refresh rates and I don't believe it's all GPU, so the CPU has to do work there too... certainly much quicker than the slow animations of screen changes on my devices.
Of course all my conjecture may be out of whack as I have no idea how Android is programed. I run my animations at .5 on my Note 4 and Note 10.1 with no ill effects yet.