Rossmann loves to rant at the camera about a lot of shit he knows nothing about. He's kind of turning into the Joe Rogan of tech.
He lost an incredible amount of credibility for me when he acted like he was a victim of Big Bad Apple siccing their lawyers on him for "selling parts."
Apple didn't go after him because he was "selling parts", they went after him because he was selling laptop and phone batteries with the Apple logo on them - labels printed to look exactly like the original parts. Something that implies to sellers that the parts meet Apple's standards, was made by an Apple OEM, etc.
A lot of aftermarket replacement batteries are shit. They have higher internal resistance so they don't charge as fast / heat up more when charging, don't have the same capacity, or they degrade faster, or all of the above. One of Apple's big successes with the circa-2013 Macbook Pro was that they used a battery that could survive thousands of cycles and only lose about 80% of its capacity. Far as I know, none of the replacement MBP batteries, save those used by Apple in their replacement program, are anywhere near as long-lasting.
Lot of aftermarket parts in general are pretty shit. Look around on the phone repair web boards and sub-reddits and you'll see talk about different grades of replacement parts. Screens, for example, can range from being terrible (poor graphics quality and poor digitizer performance) to "indistinguishable from OEM." The difference is usually at most $10, but a lot of phone repair places want that extra $10 of profit. They don't necessarily correctly program the replacement displays, they don't necessarily replace the gasket that keeps the phone waterproof, etc.
The mobile phone repair business is a shitshow full of scammers. When you realize how difficult it is to buy a used iPhone that hasn't been butchered by some clown 'refurbisher' or repaired with substandard parts, you start to appreciate why Apple engages in stuff like having screens programmed to match the mainboard.