I'm assuming there were issues with
ABD dealing with Tokyo Disneyland Resort, because they *did* offer an add-on the first year (2019). It included transportation from the ABD hotel to the Tokyo Disneyland Hotel, your room there, admission to the parks, fast passes, a free drink pass, free use of the monorail, a souvenir and transportation to the airport afterwards. But they have not offered it since (it was not offered for 2020 pre-pandemic). I'm not sure what the issue was, but it was enough for them not to repeat it.
It's different than the China ABD, where Hong Kong and Shanghai Disneyland are included in the trip. Disney owns a large (but not majority) interest in both China parks (the government of China and Hong Kong own the majority shares). However, Tokyo Disneyland Resort is 100% owned by the Oriental Land Company, and licenses the rights to everything from Disney. So I assume that makes it *much* harder to negotiate and guarantee stuff with TDLR. They had enough issues with Shanghai, and Disney owns part of it (our Adventure Guides had to argue with the folks from Shanghai, because they didn't want to allow them to wear their ID badges or carry the paddle of power, or anything that made them look like official Disney representatives).
ABD will not help you book TDLR. They aren't a
travel agency. You're on your own for that. It's hard to navigate TDLR's website, and you can't book very far in advance. But if you book an onsite hotel, I'm 99.9% sure you are guaranteed to get into the parks (you can purchase your tickets when you check in). If you wanted to wait until you're on the trip to book, the Adventure Guides would probably offer their help, but there's only so much they can do, and I would never risk waiting.
That said, we got there early the last day of the ABD (prior to the parks opening). We had 3-day passes, which at TDLR gives you one full day in each park for Days 1 and 2, and park hopping on Day 3. That's the only way you can park hop at TDLR unless you have some sort of special VIP tour. I did Disneyland Park Day 1, Disney Sea Day 2, and park hopped the last day. I left Disneyland around 8pm for a 9pm pickup at the hotel to go to the airport (I had a redeye flight out of Haneda). Obviously I *could* have spent more time there, since who knows when or if I'll get back, but I found it was enough time, and I was satisfied (and exhausted!)
There *is* a Forum here on the DIS for TDLR.
https://www.disboards.com/forums/other-lands.176/
You can also Google a couple of Tokyo Disney-centric websites.
It's a great park, and really worth seeing!
Sayhello