Contador didn't get a free pass because WADA, and ultimately CAS, didn't believe that food contamination was the true story. Many other athletes have stood up the food contamination story with much more convincing evidence and have been cleared of any ADRV.
Many? I think I recall two. It doesn't matter. The point is the rules don't suddenly change when you hit 90. If it's in your system, according to WADA (and it seems pretty damn likely USADA but I'm not reading their rules) you're guilty.
Contador didn't get a free pass because WADA, and ultimately CAS, didn't believe that food contamination was the true story. Many other athletes have stood up the food contamination story with much more convincing evidence and have been cleared of any ADRV.