We did the pricvate Rainforest Room on the Wonder in October. I visited the Rainforest room on the magic, but it was back in 2019 and I can't remember the details any longer but the Wonder kind of matched what I remembered from our visit on the Magic.
It had 3 of the special showers and 5 of the heated loungers. No hot tubs. There were also two steam rooms/saunas. Robes, towels and flip flops were provided, as well as a pitcher of lemon water and a pitcher of regular water.
One thing about the special showers. One was cold, one was kind of temperate, and one was warm. When we first got in there it seemed that none of them were warm: all coooold... we discovered we just needed to wait for the pipes to warm up before the temperate and warm showers warmed up for us.
The steam rooms/saunas also had water hoses (kind of like the ones next to a kitchen sink) to kind of cool you down while you are inside. At first we thought they didn't work. We'd squeeze the handle, but no water was coming out. After a bit, we discovered they had subtle little faucet handles where the hoses connected to the pipe/wall to turn the water on.
it was completely private. Nobody else entered the room the entire time we were in there. No attendants. Not even to replenish the water pitchers. We quickly ran out of the Lemon water, but we just poured the 'regular' water into that pitcher to take advantage of the remainder lemons.
After the first 20 minutes, we thought we might get tired of it before our 1:45 was up, but that didn't turn out to be the case.
Nobody tried to sell us anything, which kind of surprised us. After a short time inside one of our party went out and bought a couple of herbal salt scrubs for us all to try. They left us with a kind of Magic-Band device that allowed us access in and out of the room, in case we needed to use the restroom (none inside).
There were 6 of us, and we did think it was worth the money, but we were all splitting it (We had two cabins for a family trip), so it wasn't so much when we broke it down per person. We all agreed that we preferred the private experience to the 'normal' experience of waiting for people to be done with the loungers before you could claim one.