From the chip it would appear to be a hand held game. If the dealer had the face or ten up there would not be an insurance bet. I believe, but could be wrong, that in some cases the dealer would not look at the hole card until he/she plays the hand. Insurance is taken when an Ace is up. I am only a casual novice player so I apoligize if I am mistaken.

It would, therefore, be my interpretation that the joke is the frustration when you Draw a good card and loose to the hidden blackjack. Only thing more frustrating would be to have a 10 and a 6 and draw a 5 and loose because the dealer had the BlackJack. That would mean that they would then have to issue 1065 chips instead of 929