Hello,
Again, this is clever engineering from BMW. The cam followers are stuck in a way that force them to rotate.
This has the advantage to wear them more regularly and make the valve pusher to rotate also, keeping them better also.
IT has also a consequence on the wear of the cam lobes. If something goes in between the lobe and the pusher, it will be cleaned up by the rotation.
So if you have installed the camshaft properly, nothing to worry about and fear.
P.S. : the camshaft and pushers on my 1982 R65 has been running for near 280 000 km and is still perfectly in the tolerance, so perfectly serviceable....
IMHO, this make for perfect design and workmanship.