It sees homepage.spml as the default. I would guess that if you had two named homepage one with each ending, you might have problem on which one would come up. There is a benefit to using the spml ending. If you wanted to show examples of spml code like my SPML page does you name the page html and the spml code is visible. Named spml that page executes instead of displays. I could set internet config to use the html ending to execute spml code if I wanted to, but then I couldn't show you how it works.
