They should be able to as long as they haven't maxed out their 7 days of FPs which they wouldn't because they are changing out that day via a new entitlement.
What Eddie could test is this:
Book 7 days of FPs using his AP allotment.
Enter a park and use his 3 pre-booked FPs.
In
MDE, immediately pre-book his 7th day allotment for a day in the future.
Then, go to the current day in MDE to check if the FP system allows him to book three. It shouldn't because he has his future allotment of 7 total days of FPs maxed out on his AP.
It would be the only way to prove it isn't a glitch and that it is how the FP system functions when there is a never-ending supply of ticket entitlements.