Man, it's not only spread over the net. I've found the term A.H. as reference to P.H. in the tab legends of many Books (Tabs or Methods) for well known artists (metallica/vai/satriani) and from known publishers like Hal Leonard ... also other Books use the term P.H. .
It's just different ways of callng it, like 'legato' & 'hammer-ons/pull-offs' , 'glessendo'(not sure of spelling) & slides...
Don't bother urself with those terms, even if it causes some confusion for beginners, they'll gain the experience in a short while and they ain't confused no more..
Also you can't make the whole world speak one language, and I'm sure that a lot of people will insist using the word A.H. to refer to the (add thumb to pick atack) thing.