This was a whole big thing last year, and it would have been interesting to see what the committee would have done if Saint Anselm stayed undefeated last year. My guess is they still would have left them out, but it would have been a tougher decision. You can read some more about the whole deal here and here.
This year, though, we don't have that problem -- Holy Cross left the NEWHA (the scheduling alliance that Saint Anselm was a part of) to join Hockey East. That means Saint Anselm won't play the required 20 games against D-I/D-II competition, and they are ineligible for selection (Sacred Heart and Post have a couple extra non-conference games scheduled which will get them to that threshold, but they won't be a Pairwise factor).
So in short -- USCHO's Pairwise is wrong. Saint Anselm should not be included in the rankings this season. I have a correct Pairwise ranking here at BC Interruption.
Having said that, next year LIU is adding a D-I team and joining the NEWHA, which is now an actual conference rather than just a scheduling alliance. With 6 teams again, these programs, including Saint Anselm, will be eligible for selection again (and probably still won't be selected as an at-large).
HOWEVER, after having six teams for two seasons as a conference, the NEWHA should have an automatic bid into the NCAA tournament starting in 2021-2022. There are rumblings that the tournament may expand to 9 teams (with an 8/9 play in game) once that happens.