The last time we flew, they swabbed DD's wheelchair seat, the armrests, the footplates, her shoes, her hands and various places on the wheelchair frame.
Then they got out a little mirror on a stick to inspect the underneath parts of the wheelchair.
That sounds about right. For just the boot, I got just a swab, but there's so much more -to- a wheelchair, it makes sense they'd have to swab more and inspect more.