Until switching to 2.4Ghz, I coiled a portion of all my Futaba receivers (did it on 127DF, 148DF, 129DP, 148DP, &149DP receivers) so that they stay within the length of the fuselage on my all pylon racers. I always did range checks and never had any issues on 72Mhz (I never noticed the range being any less with them coiled). However I found that when flying on 35Mhz in Europe, coiling the antenna did show less range. The range was much better on 35Mhz when letting the antenna hang behind the airplane.

Frankly, as many different variables as there are regarding signal strength, ect, it's quite possible that in some installations a coiled antenna can give better range than an improperly set up, fully extended antenna. Just because you "fully extend" an antenna doesn't mean it's going to give the best reception. A lot depends on how/where it's routed in/on the airplane, ect.