Identify clothes washer part?

Granted that this can't occur during normal operation. But... is it physically possible, at all, under *any* sort of fault condition, for the dirty water to rise up as high as the opening of the fill hose? Say, if the fill-level sensor happened to malfunction, and the controller left the fill/mix valve open for so long that the washer filled up to the very top of the barrel and began slopping over on the floor... would this be high enough to allow back-suction?

My guess is that the codes are written in such a way as to require a vacuum-breaker failsafe unless it's physically impossible for backflow to occur, even under extremely improbable multiple-fault conditions.

A washer manufacturer might have only two alternatives to comply with the law: either go through a bothersome, well-documented physical analysis process to demonstrate that a vacuum breaker wasn't ever going to be needed, or just go ahead and install one. By doing the latter they'd eliminate any possible conflict with some jurisdiction, somewhere, which has a code that absolutely requires a vacuum breaker on any clothes washer.

A thorough, practical analysis of why there's a vacuum break on every washer, whether needed -- or not, and whether it serves a real purpose (other than employing repair personnel when it leaks) -- or not.

Thanks!

In the event of malfunction, there easily could be. So they must plan ahead for that possibility.

Your keyboard keycaps key is stuck, you should check on that.