My wife has mobility issues, so she usually requests a wheelchair. At TSA she's usually asked if she can stand and walk a short distance. She can, so she walks

My wife has mobility issues, so she usually requests a wheelchair. At TSA she's usually asked if she can stand and walk a short distance. She can, so she walks through the metal detector (not the backscatter x-ray), the airport personnel pushing her is let through with the wheelchair, and it's done. No extra steps or extra screening. Her bags are subject to the usually screening, but nothing extra. We usually get to go through the metal detector too. I 100% assume this is because she's using an airport-provided wheelchair which is designed to be easy to visually scan, with airport-provided personnel pushing it, and her under their direct supervision at all times. If she had her own wheelchair I assume it would be a much harder ordeal.