FYI,matching tubes is not just picking them out of the box, the testing & matching of tubes is of great importance,they are tested for transconductance,current draw & microphonics,these are simple tests that only take a few minutes with very basic & common tube testing gear.
The statement that they are matched assures the buyer that when he gets his gear he wont have tubes that are all over the place & impossible to hold a good bias,have microphinic traits & that the output level of each tube is closely matched.
If tubes are too far away from each other there will be performance issues.