People have been saying this for years, and it's one of those absolute statements that is simply untrue as an absolute. If the rotors aren't heavily scored and are otherwise in good shape, the new pads will seat to the rotors just fine if you follow the normal directions to go easy on the brakes for the first hundred miles or so.
The last time a mechanic told me they wouldn't put new pads on my truck (was under warranty so I had them handle routine service) without turning the rotors I asked what the rotors measured and he didn't know. I said "thanks, don't worry about the brakes," went home, measured the rotors which were well within spec and looked great, put on a set of premium pads, and drove another 60K miles before selling it....brakes were still fine when it left, didn't pulse, pull, or do anything other than work the way they always did.
This is simply one of those things where auto shops, with some justification, expect that the average driver is an idiot, can't be trusted to do something as simple as drive carefully to seat the pads, and they've adopted a case of CYA on just about everything. That's fine for people working on cars for a living, but it doesn't mean that the same practice always makes sense for someone working on their own car.