I’ll take Rubin at his word, but it’s very unusual to handle things that way. Usually the host will interrupt to explain on-air that they have to go to commercial, not just keep saying the guest’s name before the producer or director orders the cut. Ads have to air, but there’s always wiggle room built into live TV for a guest to finish up his point.
What is clear is that, of late, some of Fox News’s guests haven’t been behaving as the propaganda network expected them to.
Unless things have changed since I was in the business, in-studio guests aren’t usually given IFB earpieces. The hosts and anchors wear them so that the control room can tell them things like “we have to cut to commercial soon”, but the assumption is that guests who aren’t professional talent would be thrown off by earpiece instructions from a producer or director or by having a floor manager waving directly at them. It’s up to the host to give those cues to the guest in a more natural and conversational way.