I'm pretty sure that's not true. If that's the case, then a whole lot of new vehicles sold over the last few years would not be legal.
There are specs that the bulbs (and reflectors, projectors, etc.) do need to meet, and it's possible for an aftermarket LED lamp manufacturer to meet those specs. No argument that some are better than others.
@LMichaels, yeah, DRLs complicate things rather significantly, and I'm really not sure at all of DRLs simply assume incandescent filaments. I think that DRLs run with a lowered voltage compared to a standard low beam, and that would play havoc with an LED assembly that assumes a 12 volt supply. That's gonna be a frustration point for sure if you're not expecting it and don't understand it. And if I can see your headlights, general rule is that I expect them to be low beams at most
*AND* properly aimed. And sometimes... aftermarket/illegal can be good. I ran Euro spec lamp housings in my old Jeep and with 85watt high beams. They were aimed well enough and had a good enough cutoff that most people on the other side of the road didn't even realize I had my high beams on (and I was VERY careful about not brighting someone from the rear.)
Caveat: I used to work for an injection plastics molder who concentrated heavily on industrial lighting. A small part of the business was automotive, and the engineers were working on some neat automotive applications 30 years ago.