The contention is whether or not you can fix someone else’s device without a certification. If you can only fix your own device then that’s useless to 90% of people who are not technically adept enough to do it.

When I want to get a battery replaced I take my device to the repair shop and they replace the battery. I don’t ask them if they are “certified”. If they break something the liability is on them. Every single repair shop I’ve ever been to offers a warranty on their repair.