When I book at the 11 month mark in July 2019, will those points be available since the trip isn't until 2020? This gets me confused.
Don't let it.
If we had to wait until the points were obviously there, traveling in the first month of your UY would never be possible, right? Because you wouldn't be able to reserve until that month. LIke, my February trips for Princess, combined with a February UY, wouldn't be possible.
But I book in March of the year before for my February trips, because that's when I can book my home resort. I used 2019 points to book my February 2019 trip, and I booked it in March of 2018.
In previous years I've needed to bank points to help out that trip. So I booked in March of 2017 for my February 2018 trip, and I banked 2017 points (which were good from Feb 2017 through Jan 2018) into 2018 (making them usable for trips from Feb 2018 through Jan 2019), and then I booked in March of 2017 for that February 2018 trip.
Write down when each year's points are good for. So your June UY means:
2019 points are "naturally" usable for trips from June 2019 through May 2020
2020 points are "naturally" usable for trips from June 2020 through May 2021
2021 points are "naturally" usable for trips from June 2021 through May 2022
When you bank those 2019 points, you cause them to be usable for trips from June 2020 through May 2021.
When you borrow those 2020 points, you cause them to be usable for trips from June 2020 through May 2021.
So now you'll have a big clump of points that can be used for trips between June 2020 and the end of May 2021.
And those points can be used to BOOK that trip 11 months out from the start of the trip, meaning July of 2019.