Thats some really bad IT service they are doing right now. I mean, why would you need incognito to do such kind of requests?
It would appear that there were issues with Cookies that the WDW site leaves on browsers so Incognito mode solved that??
I did see a lot of folks got in via the ADR backdoor even without using Incognito mode, so perhaps those two just happened to coincide nicely for me (nicely... after 3 hours of agony).