I assume the Park Hopper Plus option works the same for these Mid-day tickets as it does for the other tickets. And with the other tickets you get an equal number of additional visits to the waterparks as you do days on your ticket (and the ‘days’ only apply to the main parks).

Perhaps UndercoverTourist explains it better?

https://www.undercovertourist.com/bl...r-plus-option/

We've just purchased a 3 day version (No Park Hopper) of this ticket from Undercover Tourist. We are going in October but only for 7 nights and we already have Universal Annual Passes so this worked out a lot cheaper for us than doing a UK 7 day ticket that we wouldn't even get the full use out of.

This would be good for us if it was the other way around as we are always in the parks for rope drop and out for lunch - I could see a problem in policing it this way around though

As you say, it would be difficult to police this. Also, I assume Disney are doing this because they are finding the mornings are a bit busier than they expected at the moment. They are trying to encourage people to come in the afternoons rather than the mornings.

Also, remember that these tickets are only valid until 15th December this year. I don't believe they've ever been sold in the past so I'm not sure that they would be on sale next year.