His logic feels wrong. Attacking at any point prior to my opponent have more than 20 cards in his deck will potentially give me a sub 93.75% chance of winning. The right answer is to just wait for my opponent to take 6 draws, then attack.
It doesn't even matter if my opponent buried the RT. It's a hypergeometric stats question. The population of cards in the equation starts at 20, with 1 success in the population, a sample size of 1, and one success possible in the sample, and the population decreases by 1 each draw my OP takes.
If he buried RT, my % chance of winning is already 100%, assuming I wait. But since I can't safely make that assumption, I know I need to force him to draw, but that's okay because the odds are massively in my favor to win at this point.
If I never attack until he has 20 cards in his library, the average of my chances to win across those 5 draws he has to make was 94.375%.
The odds aren't cumulative, at least not the way the author presents. Each turn represents a new hypergeometric equation, where the population size decreases by one. That shifts the odds a very small amount.
In other words, each draw of my opponent is a new roll of a d100, and each time I'm hoping he doesn't roll above a 93. This whole multilevel strategy is a waste of mental effort in this scenario and can only decrease your chance of winning.
Then again I could be totally screwing up the stats, but I don't think I am.