No, it’s to counteract the desire of parents dropping of their kids in front of school with their car and causing traffic jams.

Exactly. It’s a collective action problem — every car dropping off a kid incrementally endangers the kids walking to school, so if there is no enforcement whatsoever, we’d end up with everybody driving, and a situation worse than in US schools (because Swiss schools were largely not constructed with drop off zones in mind, and retrofitting them would be difficult with our land use patterns).

The original comment makes it sound like you'd get a police visit for walking with your kid to school though, which is hopefully a misunderstanding.