The 50 rounds comments was in reference to a good shoe. So a 6 deck game (312 cards) dealt to 5 decks (260 cards) is roughly 50 rounds using the 5.5 cards (rounded) per round method. No?
Yes, of course a double deck game will result in more max bet opportunities over the same period of time compared to a 6 deck shoe game. Of course that would be sitting and playing through many shuffles and times through the cards, which I don't do for other reasons.
I think I have stated my position clearly on double deck where I play. Overall, double deck is not compatible to my goals of longevity. So I won't play: any double deck game known to be a counter trap (or even suspected), any double deck game that is part of a casino chain or group that is known to pass along information, any double deck game that the casino is a known contributor to the databases. That leaves 2 or 3, sometimes 4 double deck games that I am willing to play, usually independent type casinos not associated with anyone.
So I am just saying that since I opt for a lot of 6 deck shoe games, one of the things I really like is when you get that heads up game, the count goes significantly positive, fairly early and you can score many max bet opportunities in one shoe, and not only one shoe, but one quick shoe meaning not a lot of time for an evaluation, because playing heads up for the most part the player controls the speed of the game, unless you have a very uncooperative dealer. So it is just a perfect scenario.
Now of course to get to that perfect scenario, I start playing and bail out of a lot of shoes.