Last bit of RGB changed
Unacceptable is in the eye of the watcher, so that part is tough to answer.

Distinguishable is easier: yes, there will be a difference. It will not be obvious in every frame or circumstance, but it will be there. If you simply truncate the lowest bit, it will raise the noise floor and the effect will be most evident in low light areas. So, it will look worse, but how much worse, and whether it's acceptable, depend on the particulars.