The assumption I was going with is that R and F aren't necessarily used for frame-by-frame playback.
It can be used for frame-by-frame setting of keys, especially for slot attachments, but I can see setting frame-by-frame transform values if the intended movement is especially jittery.
If you're already on the keyboard pressing R and F though, it shouldn't be a problem to toggle this behavior using CTRL+R.
On the other hand, if you use a dial-like interface device like the Surface Dial, or Wacom tablets with dials, bound to R/F, this can be a bit annoying.