I think this is absolutely true. You can see from the discussions on this forum that girls hockey is unimportant to many. And it's obvious to anyone who pays attention at any organization that, even at the orgs that really care to try to make girls hockey work, the girls are less than a second thought. It was only a year or two ago that basically every organization was giving their girls only one practice a week - at some orgs, every other week - and often they were on Sunday nights. Or late Friday night.
The reason for allowing girls to roster on an extra team is simple - to promote girls hockey in the region. And for many orgs the only way to make girls teams happen is to dual roster the maximum number of girls. The proposed rule justification says that it "could cost us a small number of girls teams". It surely will do that. What's hard to understand is why PAHL thinks that's not a big deal as implied by that wording. Of the 25-or-so organizations listed on PAHL's website, only 11 have even one girls team. And every season some teams fold while others arise, so that it's never possible to predict who will have a team or how many teams will be in a division. Because of the small number of teams, almost all girls divisions play reduced schedules - that is, the girls teams don't get the same 20 game seasons the boys teams do. The 19U division this season, for instance, had 12 game seasons. A girl who dual rosters on two girls teams won't end up playing 40 girls games on top of whatever coed schedule they have because girls teams normally don't get that many games and also because they probably won't get to every game for both girls teams either.
As for girls missing coed games, I've coached both girls teams and coed teams that had girls who missed games for their other team. As long as everyone is up front about it, that situation is what it is. Normally you are either prioritizing one of the teams over the other all the time, or you make a case-by-case call depending on the opponents and/or the importance of the game. It's not ideal, but it's something teams have been working with for a long time.
I'm not going to get into arguments about whether girls can or should play coed hockey at any level. I've long believed that girls should play coed at least through 12U because they get exposed to more players and more teams and there are more games in PAHL for coed teams as well as more tournament opportunities. I've known plenty of girls who handled 18U coed just fine. My experience is that as the players get older teams expect more and more from their players and I cannot imagine that most 16U/18U coed teams would tolerate players missing games because of their "other" team, whether the "other" team is a girls team or another coed team. So honestly I don't think that allowing girls to roster on both girls teams and boys teams is a big deal, because at the 16U and 18U levels girls tend to play for only one or the other anyway.
PAHL has to make a choice between parents complaining that their male player is getting discriminated against on the one hand and the viability of girls hockey as a thing on the other hand. Personally I think this whole argument is a waste of air because nobody is really hurt by the current rule. Regarding the Tier 1 rule, it's really not that significant. I agree with it in principle, but in practice I understand that the primary Tier 1 organization in our area generally tries to keep players from also playing on PAHL teams anyway.