I tried looking into it wondering the same thing you are saying here - and I see your point.
But if you see my quote above from the ticket purchasing page, it says:
Valid Ticket Dates
Your tickets are valid for admission to multiple theme parks on any 7 days from Oct 18, 2018 through Oct 27, 2018. Tickets do not have to be used on consecutive dates. Tickets are nonrefundable.
In that section it does not seem to be saying you have to use them on the first day - just in the window that is created by selecting a day.
It is certainly an annoying discrepancy in wording. To muddy it even more, on the updated ticket FAQ there is again no mention of “day of first use” - it simply says
Walt Disney World Resort theme park tickets purchased after October 15, 2018 are valid for admission beginning on the selected start date and must be used within the validity window provided at the time of purchase. Here are the details:
1-day – The ticket expires on the selected start date.
2-day – The ticket expires 4 days after the selected start date.
3-day – The ticket expires 5 days after the selected start date.
4-day – The ticket expires 7 days after the selected start date.
5-day – The ticket expires 8 days after the selected start date.
6-day – The ticket expires 9 days after the selected start date.
7-day – The ticket expires 10 days after the selected start date.
8-day – The ticket expires 12 days after the selected start date.
9-day – The ticket expires 13 days after the selected start date.
10-day – The ticket expires 14 days after the selected start date.
For example, a 6-day base ticket with a start date of November 1 is valid any 6 days from November 1 to November 9.
With this FAQ phrasing, the question becomes whether they are using the phrase “beginning on the selected start date” and “first day of use” as meaning the same thing - thus locking people into that first date or not.
I can kind of see it both ways, but without hard evidence to back me up, I still tend to think they mean you don’t need to use it that first selected date, just within the window. But who knows? Think we’re going to need a report from the field to see which way this blows.
(If they do mean it has to be used that first day or a change is needed, that is going to be a pain for people who simply get pushed back because of travel issues, etc. which I’m sure happens quite often with millions of people showing up every year.)
BTW, you can see in my post from last night, I don’t think the shift technique is really likely to net too much savings in any case. In some limited instances, perhaps $19 per ticket, but I haven’t had a chance to see how often that higher savings amount would occur or even what the average shift would save.
I’ll see if I can get a chance to map that possible shift savings out over the course of the year. But even if it can be done, I now suspect a purchase shift might just end up being too much effort for the payoff.