It's part of the big supplemental update they did in Japan back in March. They made it so some classes could boost the maximum level of certain PAs - I.E. you can make a Fortefighter with level 50 Twin Saber PAs, a Fortegunner with level 30 Spear PAs, a Wartecher with level 40 buffs, etc. That way, any class could (theoretically) get up to level 50 with a set PA, and not be restricted to master types. Unfortunately, the amount needed to do it, and the amount you can have max, means you could only do it with one or two weapons (and you can reverse it, you just need more points to spend in other things, then).
Don't worry though, since we won't see this for another 6 months to a year. This is just a heads-up.
Edit: Look in General Discussion for a topic named "Supplemental Update: March (I think it's 27th, could be wrong though)", that will have all your info you want in it (but might cause knowledge indigestion, due to the sheer bulk of posts in it and how the info was trickled out).
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