Honestly, as much as I like that Disney enforces full costume, I feel bad for those who can't wear more comfortable shoes, so I'm okay with SDC allowing it. I sympathize with them, as when I worked at Worlds of Fun, even though my booth was run by a different company, we still had to dress for WoF's employee dress code. With having to stand for a full 5-6 hours (we weren't allowed any stools/etc - "if you're sitting you don't look like you're working" even though as an airbrush artist, I'd pretty obviously be working even if I was sitting), it was frustrating that the dress code only allowed "shoes with laces", which meant I couldn't wear my Crocs, which are the only footwear I've been able to wear and not have aching feet and back after being on my feet for several hours.
So, yeah, if SDC allowing employees to wear sneakers means they don't have to deal with sore feet or back? I'm all for it.