When framerate gets low, the game tries to compensate by ticking multiple times before drawing. That is sensible when the source of lag is the drawing, but makes the game even choppier when the source of the lag isn't the graphics, but the mindstone.
Let's take the extreme case of the mindstone script taking a second to execute (just to illustrate), then instead of one frame per second, the game only renders one frame every three seconds (and saves basically no time relatively speaking). It also can get in the way of debugging if you can only see the prints of every third frame.
There is probably a way to figure out when it's actually beneficial to skip frame drawing and when not, but letting the user choose to activate/deactivate frame skipping is probably easier to implement, less error prone, and addresses the issue of laggy mindstones impacting the frame rate much more than they need to.