IMHO, you should not get "chunking" of the shoe material if the vendor isn't dumping a bunch of regrind scrap into the mix. Wonder if Harley is using the same lousy vendor they had for the shoes on the earlier bikes?
As for the grooves worn into the shoes (no chunking), what exactly do you folks expect? If you press a softer material against a rapidly moving harder material, the softer material will wear away. This is not rocket science, nor is it anything new. Next time you have your primary cover off, take a close look at the tensioner shoe for the primary chain. You will find two parallel grooves in that one also.
My biggest complaint, other than the cheap crap passed off by the vendor that Harley tolerates and passes off to us, is that they don't design it with enough material to last the life of the engine. Similar hydraulic cam chain tensioner systems have been used in overhead cam auto engines for ages, without all the drama and failures experienced by Harley owners. I guess if you assume the useful life of a Harley engine is 20k miles then their design is OK, otherwise they need to remove their heads from their nether regions and learn how to do this stuff right. And perhaps try doing some unannounced quality visits at their supplier's plant to look at just what kind of crap they throw into the mixing vat.
Jerry