Presumably we're also advantaged by the other team being able to set their defensive line closer to the play the ball than us

Of course it does, Phil Clark showed we give away more penalties and are not sharp enough to earn the penalties for us

once a ref always a ref - and you say fans are biased against the ref.

i never said fans are biased against the refs, fact is though as a fan we and yes I include myself because I am a fan as well, but as a fan you will spot every infringement that the opposition make, but will constantly choose to ignore the infringements the team yr supporting make.
How often do you call yr own team offside? How often are yr own team not square?
Reality is refs have no interest in who wins, and all they try and do from community up to elite is be consistent, as a fan it's difficult to see that, watch a neutral game instead.
Offside not square are penalties you generally earn through dominating the ruck in attack, we have not been very good at that for several seasons hence very few penalties

From memory it wasn't that we (and Catalans) gave away more penalties than other teams, but rather were awarded less penalties. And it wasn't a one off, either.

So to earn the penalties you have to dominate the ruck going foreword, we never did, we hardly ever earned them.