I have an opportunity to attend a conference and get a great rate at the GF in June 2021. I was aware of the park reservation system but had not been tracking availability. So for the dates I would go, no Park Res are available for any of 9 days for HS. Several days either MK and or AK are not available. I know about Park Hopping after 2pm.
How can Disney sale rooms or tickets with this kind of limitations? What am I missing?
When you book the room they make you aware of what’s available. Some people don’t care to go to all of the parks, or are fine with just hopping to HS in the afternoons. That’s what we’re doing this trip.
Could be the reason for the great rate 
I mean, it’s publicly available information before you book a room or purchase tickets, I’m not sure what you expect them to do? Not book hotels or sell tickets if one park is fully booked for a day? That seems like it would be more problematic than the current system (fully disclose the park reservation availability prior to purchase).
All the other parks are available.
They can because you agree to their terms and conditions when you enter the contract with them buy booking the reservation or buying the tickets. Sucks their is no availability, but it’s completely legal for Disney.
Also they could release more or it could open if you keep Checking. All Hypothetical so I wouldn’t book if your not happy with what you can definitely have.
But I get what you are saying. Unfortunately COVID has put a lot of limits on things.
Concur: checked this morning for dates and parks and didn’t find what I wanted but checked now/PM and voila I was able to make a park reservation. I have been watching for a few weeks and things have changed a lot
Oh good! Was hoping someone with real experience would chime in! I’ve def read people having success.
And there’s been NO HS openings this week for APs and now there is tomorrow. Wasn’t there this morning. My problem right now is the 3 park res limit.
I was there last week and could not make a reservation for AK. I went to GS at Epcot and they were able to move our reservation from HS to AK for the next day! I think they were as shocked as I was that we were able to get HS but not AK!
Related question - should I be concerned about EP availability the first week of June? Right now my plan is to hold my HS reservations to see if I get a ROTR BG, and if not, switch to Epcot. However, as OP points out, those park reservations are booking up way further into June than I expected at this point in April. When I checked the other day (first time in a month or so), I said WTF loud enough that my wife came into the room very concerned. Not sure what to do…
EP has not sold out very often compared to the other parks. I think it’s last to go.
Yes, but this does not help my anxiety 
I think I’m going to have to just bet on getting a BG by day 2 and switch my day 3 to EP (I currently have 3 HS reservations and no EP)
ETA: Also, day 1 and day 2 are Sunday/Monday of Memorial Day weekend. Big crowds? Maybe. Maybe not… I know Sundays are usually the best for HS, but I dont know if thats true anymore. I’m optimistic that I’ll get a BG on day 1 but my boys are obsessed with SW right now and I want a second chance for ROTR (or third chance if needed)
ETA2: Sorry for the rambling. Every time I start thinking about this again my head starts spinning!
For the first full week of June 6 - 12, Monday-Friday, EP is the only park with reservation availability. And the MK only has Saturday open. Disney is making this info public and it is not illegal, etc., etc. but buyer beware. They have far more hotel inventory available and a very limited park inventory to sale. And that is not appealing to me. I was just real surprised at how tight the supply of park inventory had gotten. How concerned should someone be that Park Hopping is going to be a problem on that Monday - Friday when EP is the only park available every day until 2pm.
Somebody else may be able to answer this better but from what I’ve seen other posters say, it doesn’t appear that park hopping has been restricted at all even if all the park reservations from a particular park are gone. So, for example, there have been no reports of people being prevented from hopping to HS even on a day where all the park reservations for HS were booked.
That is correct. Even during spring break, no park has been reported to reject hoppers on any day. I doubt it will ever happen, with the exception of the October 1st anniversary.
I have in my brain that Disney guarantees that as a resort guest you will be able to get into one park each day of your visit. It may only be EP, but there should be at least one available.
No they don’t guarantee that.
They used to, pre-Covid and before park reservations. But now they warn you before booking that you must have a park reservation to enter a park. And there is no guarantee of one.
I had friends who went over the Spring Break. They had reservations for most, but not all, days - simply because they couldn’t book anything.
Maybe by then more capacity will be allowed, too. 