Yup, that's the site that officially doesn't create iPad prepaid accounts anymore. Glad to hear that the reality is it still does! Though, despite all that, it still seems much harder than just going to the AT&T store and asking for them to give you an iPad prepaid SIM, that's already provisioned and you just need to click through on the iPad (no Wi-Fi even needed).
Also, I don't live in an area with AT&T LTE, but are you telling me that LTE is working with a non-LTE SIM? This surprises me as I thought non-LTE SIM cards didn't have the necessary service tables to find the LTE network! But again, I don't live in an LTE area. Here is a site with a picture comparing an LTE SIM and the previous SIM before the LTE SIM (note that these are 2FF SIMs, but the MicroSIM for each looks similar just smaller):
http://widgetfolder.com/lte-sim-card-is-coming-to-at-t/