Interesting information from 41magfan. From my experience, going back to the 1970s, the 7 yard line was a part of the PPC course (which has several variations itself). Cooper notes that early competition rules dictates a competitor @7 shoot”one handed, from the hip”. High probability that “Jelly”Bryce influenced this style. Prior to the late ‘50s, military training generally was “bullseye”, notable exceptions being Sykes/Fairbarin and others prior to WW2. They specifically eschewed competition, but wrote about training with targets close(3 yards).
JMHO, but I think the distance between drivers side car doors “back in the day”was an influencer(7yards). The distance appears in the first PPC matches in the 60s, and many ranges were built because the range personnel were PPC competitors.
I have little to contribute about 15&25 yards, except to note they are distances specified in PPC. Cooper specified 10 yards for the “El Presidente”. In the 70s in US IPSC, shots were rarely closer than 7 yards. The South West Pistol League pushed shots out to 100 yards(!) rarely, and there were some shots at 50 in LE quals/PPC. Cooper and others stated that a competent shot should be able to deliver a “center” hit@25 yards in 2 to 2.5 seconds from the holster-so that reinforced the 25 yard “long range” distance. Further reinforced by US Special Operations personnel recommending transitions to handgun(from long gun)25 yards and in if long gun out of service.
Karl Rehn of Austin TX has done a study on courses and gear and he might contribute.