I don't think it matters if they're matched or not. As long as they are the same brand, from the same vintage. I bought 4 RCA 6DE7's from tubedepot.com awhile back and I highly doubt if they are matched. I cant detect any imbalance whatsoever.
volume discrepancy between pairs with more than 20% difference in
transconductance using the tv7 d/u. for example 75/48 and 56/36 for a 6de7.
(using a bias probe and multimeter is much more exact since you'd be getting
reading at the amp's operating voltage...) the volume difference wasn't very
great but it is noticeable and can be somewhat annoying.