I have no info on that resort but it has been my experience in hotel stays, including Disney resorts as well as Holiday Inn & Hampton Inn, roll-in showers have always had a built in seat. Accessible tubs have grab bars but not always a seat.
I'm like you though, I would want to know for sure. After a recent road trip with less than adequate seats even in roll-in showers, I've decided to always travel with my own shower seat. If I end up not needing it, my husband won't have to put it together. I would feel almost positive any new hotel would have a suitable seat in a shower room.
On our road trip, we stopped at a Holiday Inn & was offered a choice of either a roll-in shower room or tub room. We asked to see the rooms. The shower room had a nice built in seat but no hand held sprayer...the wall sprayer was on the opposite wall. They showed us the tub room which had a nice hand held sprayer but no seat. I made the mistake of not bringing my own seat on this trip. My husband ask for a seat, they had none. I noticed the shower room looked like the sprayer had been removed because the connection & holder was there. We ask if we could take the sprayer from the tub room & install it in the shower room. The desk clerk didn't know how so my husband did it. The desk clerk apologized & said the last guest must've taken the sprayer. She was going to order one. We suggested she also order a seat for the tub room, pointing out that anyone needing a handicapped accessible room would probably need a seat. After that frustrating trip, I'm glad to get back to Disney in March.
I really feel that any accessible rooms should provide a good sturdy shower seat, whether it's a tub or roll-in shower. Holiday Inns have a Keurig in every room but can't have adequate equipment in two HA rooms. I've seen complaints on the Disney Vacation Club forums about smaller coffee makers & no DVD players or clocks. I don't expect Disney to provide shower seats for unlimited numbers of guests staying in regular rooms but I don't think it's too much to ask Disney, or any resort to provide a good seat for all accessible rooms. My seat, which is the transfer bench type, cost less than $100, so about the price of a Keurig. We have to travel with an extra huge suitcase to bring my own seat.
Several times we've had to make do with non-accessible rooms if no HA room was available. In those cases I'd expect to have to supply any equipment I need to make that room work for me. Any guest booking a HA room should not have to worry if they'll be able to take a shower in that room. At least a good sturdy shower seat should be provided. I realize some guests may require additional, or specific types of equipment that they would need to bring.
Sorry for the rant, I've just been in the OP's position of trying to get a confirmed answer on what equipment to expect in a HA room & feeling that to be safe, I should bring my own.