As a similar story, I was recently playing blackjack next to a casino war table. I kept hearing laughing and commotion so I looked over, turns out the dealer had dealt everyone blackjack hands, and it may not have been the first time she had done it. When the pit boss came over the dealer reiterated that it was her first time dealing war. Not that it has much of a learning curve, but as in your example, old habits die hard.
Anyway, a dealer who had learned it but never dealt it was brought in. A pit boss stood close buy, but because the pit boss was watching other tables too, often I was the one telling the dealer what to do.
After a while, the pit boss realized that I knew what I was talking about, and actually left the area, leaving me 'in charge.'
Have you had a dealer that was clearly dealing a game other then the one they usually deal? I was recently playing BJ and my dealer was a very nice Asian woman who clearly typically deals Pai Gow Poker. On one of the hands, it was a push 17 to 17, however I had a Q7 and she had a J7, and she paid me because in Pai Gow Poker I would have had the higher hand, and I guess it was just automatic for her. Funny but true.
I deal monte carlo night type games part time. I usually deal bjackjack but from time to time I get puton hold'em. It is not as easy as you would think. Cards down instead of face up, no dealer cards, etc. Yes, very simple, but when you deal your mind kind of goes into a dealing zone and any intrusion is unwelcome.