The cross breeding to introduce this dilute color can be many generations back, allowing a DNA test to not show it. Most modern canine dna tests can only successfully trace back 3 or so generations. This is how a lot of people claim their silver lab is “pure”

This is the same phenomenon with a lot of “out of standard” fad colors such as the merle frenchie, and so on. It’s easy to either produce hung (forged) pedigree papers, or claim pure lines through DNA testing. We just don’t have the technology to trace back more than a few generations