Good find! In my experiences, in rural communities where dirt/gravel roads/paths are common, and marshy, wet terrain, removing shoes upon entering the classroom is common. It also saves on custodial costs, with floors needing less frequent cleaning.
After working in a program for early elementary students with autism, I can totally see him walking off to the brush line, shedding his shoes as he walked. I worked with kids who only wore one particular pair of shoes, and if they had to wear a different pair (say their regular shoes were destroyed, or covered in mud, or in the washer), they would be taking the imposter shoes off all day. I worked with kids who refused to wear shoes at all, and kids who refused to take their shoes off for any reason. We worked with them all to gradually accept the wearing of or removal of shoes.