"But he's..." Phalanx begins, but it almost seems as though they hadn't actually meant to make words happen, because they trail off before they go anywhere.

If they'd been a creature with any amount of social awareness at all, they might have been intentionally catching themselves, but that's a low possibility in this case. Phalanx doesn't even think to move over so Vincent can easily get off of the couch, let alone probably think about the words they may or may not be saying.