Ok, they have 2,3 or 6 patterns to choose from and randomly select one. Someone knows those patterns. They pull tapes to verify the pattern is correct, against the master pattern that is known to "someone who is bowling in the tournament". Someone bowling in the tournament always knows. That is the problem.
Eric Pierson who used to design the patterns for the tournament, bowled in the tournament. There is not an independent party that does not bowl in the tournament designing the pattern.
And lets be realistic here. It's nationals. Take 8-10 bowlers of the same hand and burn in a shot around a defined point and if you are good enough, you will be top 100 most years and if you guess correctly, top 20.
Most of the good teams come from the same areas, Wisconsin, DFW, and current and former college teams, and other teams here and there. Why, those areas have some of the best bowlers in the country, because college programs don't bowl on THS. Wisconsin constantly runs sport leagues and tournaments, and DFW has the ITRC where you can practice on any sport shot you want, and several houses will also run any shot you request. And since USBC relocated there, a lot of the best bowlers in the country, moved there.
You could hide the shot, and within 2 weeks of the tournament opening, the internet will know where to play and how long the shot is. How, someone will go and watch and put it out there. And teams will immediately start practicing.