I am having the same issue. Unfortunately I manage our web filter, and I will NOT open www.apple.com for the same reasons your director won't. This is a hospital, and we have MANY iPhones here that are used primarily for accessing our Intranet, in-house mail server, etc. We shouldn't even have to verify Internet connectivity JUST to use wifi.
After connecting to wifi, iPad checks to see if connectivity to internet is possible, and/or if further login is required. To do that - it checks connectivity to www.apple.com . If not - it assums wifi is no good to you, and switches back to 3G.
There is a valid reasoning behind it, but indeed, it sounds like there are scenarious in which there should be option to disable this...