aftermarket batteries are AWFUL though, I played that game with my Thinkpad for a number of years before sucking it up and buying an OEM replacement. I was lucky to get six months out of an aftermarket battery and sometimes they were out of balance and dying within a matter of weeks. And once the OEM supply is truly gone (or aged out of existence) you're done anyway, unless you crack open the pack and replace the cells yourself.
The way you replace a MBP battery is you take it to apple and have them do it for you. It makes absolutely no sense to pay to have it cracked open and serviced and then put a $30 ebay shit battery in it that will fail in 3 months - which if you're not going to an apple service center, is probably what you're getting. $200 isn't cheap but a genuine lenovo OEM battery (one which even still may have been sitting on a shelf for years and the cells are no longer at their best) will cost you about $125 from a legitimate source. $200 for a fresh battery with installation isn't really all that bad. For something with a 3-5 year lifespan, that's just the cost of using the device, same as a phone.
I like serviceable devices too, and I think the parts should have to be made available to the market, but batteries and screens are two areas where I "get it" in terms of the protectionism around parts supply. There's a huge difference between the OEM and the aftermarket parts in these areas, and customers are going to want to know why YOUR device is draining THEIR battery in 30 minutes all of a sudden. Don't you know they just had the battery replaced last month!? It's YOUR fault! Regardless of whether it actually is, you've got a lot of extra service work and a lot of upset customers. Louis Rossman is a cool guy and I'm sure he personally is careful to only use legitimate parts (or at least be upfront that it's not an OEM part) but he's only presenting his half of the story there.