I would say that it’s very much their intention. When you’re using alias paths for SEO, you don’t want .html in the path. Imagine this if "Products" is your folder:
bogus:
mysite.com/products.html/myfirstproduct.html
normal:
mysite.com/products/myfirstproduct.html
So I’m pretty sure you’d be outvoted on this. But I would question the need for using ".html" at all. Take a deep breath and ditch the ".html" altogether.
final:
mysite.com/products/myfirstproduct
But if you’re doing it in Revo BE CAREFUL. Don’t delete the whole HTML Content Type, only the extension (I made that mistake and crushed my whole site and had to go into the blessed database to fix it - others have too, I saw a guy do it last week). They will supposedly be guarding for this in future versions of Revo. Instead, you click on the extension and edit there - no helpful prompting, unfortunately, you just have to know.
Cheers