[tssva]

The grey market didn't put the logos on. The parts in question were screens where the glass had been broken but the display panels were still functional. The glass was replaced and the units are sold as refurbished. The Apple logos on them were on the display panels and placed there when originally manufactured for Apple.

[monocasa]

This. A lot of these "counterfeit" parts are just official parts that have been refurbished.

Take a broken iPhone, part it, replace the glass, now you have a refurbished screen to go in someone's broken iPhone.