While the post you linked is made by a ROBLOX admin, I do want to mention that it is not only made in 2021 but that there has been a lot of research done on this. I would also like to refer you to this post, here. What's better: Hollow or filled terrain?
I do understand the concern with this information though, and will add on something regarding it. I also almost forgot something I wanted to mention about water in this post.