I have seen it. I had a F-150 on our farm growing up and when I'd remove the filter the tube would have dirt over the inside. However I was in dust that was extremely thick.
Well now, that would (and does) cause me great concern.
If you found any dust in the intake tract, you can rest assured a great deal of ingestion has taken place. Not a good thing, and Hell on rings, and cyl bores.
As I said, I'm not a fan of the product, but this has always been from the standpoint of they are a PITA to clean and correctly oil, not because of poor filtering.
My older son owns a demolition co. all Caterpiller equipment.
He and I share a somewhat fanatical belief regarding the capability of OEM air and oil filters, IE, its all we'll use.
When performing filter service on his equipment, we have never found any evidence of ingestion.
And, I'll tell ya, the dirt that pours out of those 3ft tall filters can be measured in pounds!
BTW, these filters can and are dry cleaned about 6 times before they must be replaced.
Anyways, if any who are following this thread have found evidence of ingestion, please report it.
I'm serious as a heart attack when I tell you this will cause unimaginable wear that would not be considered as warranty.
A truly interesting read,