Ahsoka could and would have wiped the floor with him at fourteen, never mind as an adult. One just had to be mature enough to be allowed in war.

Vader himself is only taking the occasional note - the regional phrases he doesn't know, weapons he isn't familiar with, so on. The rest? He commits to memory as if it's been beaten into him to never, ever, make someone repeat themselves.

That trait far predates Palpatine being his master. By two decades.

Once it was concluded he waited. Silent. No he didn't have much patience. Teenagers generally had even less.