Presumably a high volume and skilled third party repair shop and its purchasing people will be a crucial role in buying and distinguishing between the two types of hardware.
To some extent words mean what people who use them intend to mean, but in my opinion we shouldn't be calling parts from the same production line counterfeit, because the word implies forgery.[2]
1. https://en.wikipedia.org/wiki/Bootleg_recording
2. https://www.dictionary.com/browse/counterfeit
Edit: changed a word for clarity.
If they had a particular QC standard marking, but had not been manufactured in accordance with that level of QC, that would be forgery, right?
If they bear the trademark of a company that demands certain QC standards, but were produced without those checks, it seems like the same thing in a way.
You don't have to do that.
You're probably partly right some of the time, and my perspective probably has some value perhaps maybe.
I respect that a lot.
In the absence of a legal after market or licensed / genuine / third party parts ecosystem, this is, or should be, the expected natural response: off license / bootleg / counterfeit parts ecosystem.
In my opinion, then, the fault lies with Apple, and / or the absence of a regulated market for those parts and the necessary documentation.
People will find a way to source what they want. How you approach or deal with those problems is probably a political / ideological thing.
Saving the planet is far more important than protecting the profits for replacement parts. Of course they shouldn’t be allowed to sell complete phones but selling screens is good.
For an interesting contrast, look at the automotive industry, where (with the exception of perhaps some newer companies/models, like Tesla et.al.) there is a thriving aftermarket which is so complete that for certain models of cars, you can likely build an entire powertrain and even rolling chassis using zero original parts. Entire engine blocks, internals, transmissions, axles, suspension, brakes, even frame rails, can be bought from the aftermarket. Of course a lot of these parts are enhanced and marked with different manufacturer's names, but the OEMs themselves have in general not minded and sometimes even encouraged the aftermarket.
The other very common possibility is that it's what's called a "ghost shift" where the factory runs a whole production run on a possibly overnight work shift, creates a batch of product for sale to third parties, and then resumes their legit-for-transfer-to-apple production run the next morning. Happens with all sorts of electronics manufacturing in mainland china.
This does not necessarily mean that the ghost shift products go through absolutely the same level of QC that the main production run gets, but I wouldn't call them counterfeit.