Not entirely true, but it is a lot less work and mess if you don't go too far.If you loosen it too far, that's it.
I had to use four layers of wax paper to get a leather holster's retention right for a Kahr.Plastic bags or wax paper work. I prefer wax paper (1 or2 wraps) as it also "lubricates" the holster. Wrap the gun and insert in holster, let sit overnight. The next day draw and reinsert gun several times. Repeat if needed.