If you get into one round of testing you're automatically into the next unless they decide to exclude alpha testers and have us sign up again. Otherwise, it goes like this:

Play FFXIV? If yes - remove from pool. If no - send invites.

Have a capable PC? if yes - remove from pool. If no - send invites.

Want to play the game rather than test and make it better? If yes - send invites If no - remove from pool.

While they do want to get a wide array of players and systems, they usually invite the wrong group of people. This is true for not just SE but many other companies.