I don't believe this is supported by either logic or fact. Having sub-optimal recovery means you're sub optimal. That premise would make a "no chain" day a bad day.

"Openers" is "open" to definition. Ideally it's an effort that loosens up whatever tightness might have developed on a day off (presuming you took a day off), allows the rider a chance to prepare mentally and visualize, work on form such a sprint timing or TT pacing or position, and has little/no impact of fatigue or muscular integrity. How you go about that is individual.