I wonder if there's some functional issue as to why they cannot book on the
MDE app. Making them line up for a kiosk in the park would be a dealbreaker for me. That has the potential to eat up a lot of rope drop time.
I'd venture to guess that it's due to resort stays, since those are currently the trigger for FP+ availability during the test. I don't think MDX plays very nicely with non-Disney reservations (it rarely plays nice with Disney reservations made through the app itself!)
If they have MYW or AP, they are supposed to be able to...but I wonder if they are just trying to test the kiosks with a larger group before they unleash it on the public. I'm betting that the Swan/Dolphin reservations system can't be integrated, so they'd be unable to distinguish between S/D guests and anyone else.
The load/crowd testing of the kiosks is interesting. While I was there last week, the kiosks were almost always empty since everyone had MDX availability to book and tweak. There was pretty much always someone at Guest Relations being walked through though, and that was absolutely a lengthy process.
Judging from that process and the CMs' involvement with them and the few and far between kiosks I noticed (in MK, I only saw 2 screens in Fantasyland and 2 in the tunnel between Adventureland and Frontierland near Aloha Isle), this has the potential for a mess.
(Note, I didn't notice any at the other parks, but I also wan't particularly looking for them.)
In any case, the results should be...interesting.
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As far as my predictions since no one asked?
MBs free to onsite, $40 per guest offsite. Disney will want to monetize the bands even more than they are now and there are reports (and I heard several people ask myself) if people not part of the testing could buy them. I don't think Disney's going to want to miss that opportunity.
FP+ prebooking available to all, with perhaps a +n perk for onsite guests (assuming they can ever get the functionality working correctly...it's still very flaky with ADRs). There is no need for FP+ prebooking to be limited to resort stays, since it's all based on the ticket media and not the resort. Under a ticket-based system, MM+ doesn't have to care about where you're staying, as the system remains the same across the board. A +n perk would be enough to satisfy most onsite guests and is a system already proven to work (there are many who consider the +10 perk for ADRs as one of the high ranking reasons for doing so.)
There's also the issue of the kiosks themselves. Allowing prebooking for all distributes the processing over time and across a multitude of devices, rather than forcing them all to use the same few kiosks in the park. This has several beneficial effects for Disney including reduction of CM support time, reduction of wear and tear on the kiosk hardware, reduction of guest dissatisfaction from standing in yet another line, and limiting exposure to kiosk system crashes. (I'm a bit too cynical to believe they'd do it primarily for the guest purposes, but it makes sense for them to do it from their perspective.)
There is no loophole to it, Fastpass+ is depends on ticket media and Annual Passholders have ticket media.
Except, the case in question was new tickets and not APs. Of course, this still qualifies as having MBs (moreso the MyMagic+ system that MBs are a portion of) activated by a previous stay as well as having valid ticket media, so it's similar, but slightly different than the intended use case.