most likely. looks like a softcover book, which tend to have more errors than the hardcovers and are never really corrected/erratad, which is probably why you don't see a fix there.
I think you are confusing always with usually. Specific overwrites general so it is quite possible for an outsider to have a different HD than typical.
That said, in this case it is quite possible that it is a mistake. The particular book that that creature was printed in came out just as Pathfinder came into existence. Almost certainly it was written with the 3.5 rules being more familiar, and was indeed branded as being 3.5 compatible. In 3.5, Outsiders typically had d8 HD.
In 3.5, Outsiders typically had d8 HD.
It's a 3.5 book, outsiders did have d8 HD back then.
Winner, winner, Belkzen dinner.
The writer of the book said it is Pathfinder, not 3.5, so no Belkzen dinner for you.
Actually that thread says it was written for 3.5, decided to be published under the pathfinder name at a very late point in the process and that some conversions were done at the last minute to make that happen, and a few things went wrong.
So yes, the fact that outsiders had 8hd in 3.5 and 10hd in Pathfinder 1st is certainly the reason for this.
The writer of the book said it is Pathfinder, not 3.5, so no Belkzen dinner for you.In 3.5, Outsiders typically had d8 HD.It's a 3.5 book, outsiders did have d8 HD back then.Winner, winner, Belkzen dinner.
Ouch! They wrote it for 3.5, published it for Pathfinder RPG, and forgot to actually convert a bunch of stuff. Well, they were likely in a hurry....