I've already found with a DID ZVM chain and a Scottoiler that there is no need to adjust the chain between tyre changes (about 5500 mile fae me). On a chain that has done over 20,000 miles I can't measure any wear.
So I'm not that surprised by BMW's claims.
The problem is you still have sprocket wear, in particular the front sprocket. Mine was starting to look a little spent after 12,000 miles. So I just popped in another (20 quid), I didn't bother fitting a new chain (170 quid) or rear sprocket (45 quid).
So have BMW also invented almost ever lasting sprocket, or are they advising you swap out the front sprocket now and again - and how many times?
https://www.motorcyclenews.com/news/new-tech/bmw-m-endurance-chain/