The video shows the amount of magnetic material captured by four (4) magnets widely spaced around the pan after ~135,000 miles.
Three (3) ways non-metallic material is captured in a sealed transmission are: (1) very fine particles remain suspended in the fluid, (2) some particles cling to the pan and strainer and (3) large particles that would bind in close clearances are captured by a large surface area strainer that is likely to hold a lot of material without significant flow restriction.
These are robust design details that contribute to legendary Toyota reliability.
I rarely incur special operating conditions, so I recently exchanged 12 quarts at 114,000 miles and didn't open the pan. I'm planning to wait until 180,000 miles to inspect and back flush the strainer with used ATF, replace strainer o-ring, clean the magnets and pan.