While I haven’t been on this excursion, I do live there so I can take an educated guess based on the description. Hopefully someone who has taken the actual excursion can clarify for sure based on their experience.
The vast majority of this will be a sightseeing tour by boat. While it does mention the ability to get in the water at Stingray City, it talks about a “quick dip” rather than a stingray interaction. And looking at the route, and that it’s a 3 hr excursion, I’m guessing you’re at Stingray City for a half hour or so, tops. Might have a bit longer at Stingray City if they just take you into the canals where the big homes are and point out the mangroves that line the entrance to them instead of taking you into the nice section of mangroves on the far side of the marine park. Might be a good excursion for someone who would prefer to stay on the boat anyway, and for those who want to see more of this very beautiful island than just Stingray City.