We're currently fighting to get this definition changed to 100/100 symmetrical, because as you say this magic number of 25/3 lets DSL in the door, which in turn means incumbent providers can continue to get federal dollars that they will refuse to spend on infrastructure. Telcos will claim their ancient 50 year old copper is capable of delivering 25/3 to an area, when in fact only the first 5 houses on a road get near that number. If you happen to be the 12th house down the road (about a mile out) you get 7/1 on a good day because the copper was strung in the late 1950s. The minimum standard having a symmetric speed requirement prevents small diameter copper from stealing money from the pot.