Why are they measuring?
Whenever I'm in the metropolis there are shed loads of Oyster card users. They are giving up info about entry and entrance to the underground system. And if you have an Oyster card I'm guessing you are fairly knowledgeable about the optimal routes through complex stations.
I don't know if 1 day travel/capital type and normal (single / return) type tickets can be tracked in some way so perhaps they are are only indicating general numbers through stations, not station to station journeys.
Perhaps this helping with measuring flow around large stations once you are outside the actual barriers.
Wonder if they are considering having coffee and sandwich shops inside the system (barriers) for those that are waiting, but only know they are waiting after passing through the barriers. That would suggest the possibility of trains being delayed until enough mocha-latte had been purchased.