Acknowledging is kinda funny in that it's like marking something as "read", or "receipt confirmed." It invokes notification, even if the original attempted contact wasn't necessarily proper or valid.

I don't think you ever have actually acknowledge any reserve assignment. But NOT acknowledging it doesn't make notification any more, or any less, valid.

I'm quite sure you could call the VRU (or check iCrew) post-rotation, hear (or read) a valid assignment, and acknowledge nothing. But whether or not you acknowledge it doesn't matter when you either show up to the legal assignment, or no-show it. If it was legal notification, you're responsible.

I do acknowledge things that I know are 100% legal, just to "clear my inbox" as it were. But I don't HAVE to, and not acknowledging doesn't make a legal assignment any less legal. And acknowledging something that was an otherwise invalid notification could make that notification potentially valid (Like acknowledging an assignment following X-days 2-days prior and effectively resetting your 30/168 window.)