> Trying to explain D&D's shitty writing
> When GRRM gave up on them and just told them to 'roll with it' they rolled over the half finished book 'The Winds of Winter' in their custom 20 million dollar Range Rovers until you got the script for Season 6 Game of Thrones.
Nah I've actually liked this season a lot in all honesty, but you can tell that they're cutting corners and rushing to the end. I think Arya's scenes dive in quality was due to some major changes by them, and trying to explain it with in universe logic won't work. Instead of rushing properly, they dragged certain parts out to give Episode 8 some shock value to remind people we're near the end of the season, especially since Riverrun didn't end up like the siege of Kings Landing.
I think the waif's done for, and any new skills displayed by Arya will be explained as off screen teachings. The purpose of her Arc was finding herself. She went from pretending to be a boy, pretending to be some lower nobles daughter to Tywin, eventually struggling with whether or not she hated the Hound and if she was his ally or just a political hostage, to pretending to be No one. She's confident in who she is now, now that she has passed the absolute test of identity.
As to her lessons, She might even ramble off some stuff she learnt to someone, maybe a Stark Family member when she returns home. In the books she learns languages, poisons, and how to be stealthy, not just how to fight. Because really, fighting is one of the last things the Faceless men should be doing.