I'm so used to seeing gate info on flight status searches when flying B6 that I didn't realize they're apparently non-existent for EI.
However, there is this from EI's own website last year:
https://www.aerlingus.com/travel-inf...rminal-change/
Our daily service to Boston, since May 2nd 2016, is arriving into and departing from, the recently upgraded Terminal C at Boston Logan Airport.
I'm assuming it's entirely possible Massport hasn't updated their signage terminology since before per-clearance existed! Or they just felt it was too complicated to add "except for pre-cleared international flights which may arrive at any terminal in the airport depending on carrier."