I would say you're mostly right. The margin of error is bigger than I thought it would be, after checking myself here. Also some states do equip their state patrol with vehicle-portable devices that are not the handheld. Depending on where someone is, they might not get a choice to take it at the station instead (that seems to vary quite a bit by jurisdiction just at a cursory glance). But ultimately I support the philosophy of giving cops as little ammunition as possible. Just make sure you can actually do it.