23 Sequoia 19K change rear differential oil with surprise

23 Sequoia(produced at Dec 22) on 19K miles, changed rear differential oil with VALVOLINE SAE 75W-90. I think transfer case and front diff should be fine so only changed rear diff.

There're some dust on the magnet, most of them are mud but some are very thin metal pieces. And dirty oil looks like metal flow.

Surprised that even only got 19K miles but so dirty. Is that normal?

Parts links:
Oil:

$63 Valvoline Flexfill SAE 75W-90 Full Synthetic Gear Oil 1 QT, Case of 4

https://www.amazon.com/dp/B08K9CGB6Y?ref=ppx_yo2ov_dt_b_product_details&th=1

Gasket:

$9 Rexka 24pcs Transfer & Differential Service Gasket Kit Compatible with Toyota Lexus 4Runner Land Cruiser Tundra Tacoma FJ Cruiser Highlander RAV4 Sequoia Sienna 1215710010 9043024003 90430A0003

https://www.amazon.com/dp/B0BFGB3GPM?ref=ppx_yo2ov_dt_b_product_details&th=1

 

Differentials are always pretty dirty on the first change. That’s actually not bad, my rear gear oil was dirtier than that at 30k miles.

 

All differential gear sets will wear in resulting in what you see in the first change. Just most wait until 100k+ so it seems more normal to them