There are EU bits that say Stormtroopers know how to fight but I don't see much reason to pay attention to them.
Okay, I'll bite - what leads you to this conclusion? And I'm not asking flippantly, I mean it sincerely - what on-screen evidence has you forming the hypothesis that Stormtroopers are weak in combat?
Him being right leads him to that conclusion, obviously.
He gets to choose which bits of the EU count as being accurate, no one else does.