In my case I've had an application (pending) for alpha client testing for over a month, playing since season 1, never had a punishment on my account (except once for leaving (losing connection) - which I do not believe falls under "negative in-game behavior" category), +160€ worth of rp bought (, filling out surveys asking for feedback whenever I get an e-mail asking to do so) and being active.
And from what I know that isnt the worst either, I know people that have an application (pending) for over 3 months now. With pbe I've had an application since they started accepting them (after they werent really "public" anymore).
I dont know anyone from NA, so I cant directly speak out if they are getting their accesses or not, or from any other server. But from what I've noticed there are no complaints in comments from recent post "Become a League client update alpha tester" on NA site, but on EUW+EUNE there are lots of them.
In a alpha client FAQ you are mentioning in the first sentence that you are looking for players from all over the world (in "WHAT TYPE OF PLAYERS ARE YOU LOOKING FOR?" tab).
But it does look like NA players have quite a priority to me and I would like to know why riot decided to do so, its not like I would be mad at them now, where would be a point for me rioting against... riot ? I am just asking out of curiosity whats the reasoning behind it, so then I can form a valid opinion about it.
**OR** maybe there is more to the algorithm (since I dont believe they would have employees hand-picking people) that is selecting the players to test pbe/alpha client and then I would like to know what it is, since I am starting programmer myself.