In my experience with 4 Tundras, Silicon stays relatively high until after the 30K miles mark. This oil started service around the 20K miles mark, so it's right on schedule...It's due to the sealers used internally
Overlooked the 30,000 mi. Given the numbers I would have expected that run started later than the 20,000 mi it did. That explains the lack of any sign of abrasives.
All things considered I don't see how you could expect better. Looks excellent.