Ah, on closer examination, this wasn't the old issue which was fixed, it's just a case of circumstances causing the phasewall to get tuck in the open position (it's darker but you can see the different color of the tile there--that's the appearance of an "open" phasewall). In their open position you can fire through them, but they still won't let you move through that space unless you have Structural Interface. If another enemy passed through it would be detected again and close, but they don't otherwise close on their own if they managed to miss the closing trigger due to special circumstances. (This can happen with regular doors as well, but the more unique properties of phasewalls might make this stand out more, also being as rare as it is.)