Yeah it is, because it has NOTHING to do with actual gameplay. Reading a walkthrough or learning tips about how to actually play is much, much different than manipulating the game to increase scores. Saying that helps you play better is totally off, how does it?
It lets you learn the game at a slower speed, which lets you formulate strategies for playing normally. I do it on hardware in a way. I practice DK and DK Jr. at the higher levels, because having to waste time on the earlier levels wastes valuable practice time. I sucked at Moon Cresta until I started to set it to easy to practice. Then I figured out the enemy "patterns," which I was too busy dying to figure out on normal, and can now regularly finish one or two complete sets on normal. Playing E.T. or Adventure on 2600, you can really get the hang of the game at the simple difficulties, which is necessary if you are to have any chance at the higher levels.
All practicing on an emmulator would be doing is letting you formulate strategies and plans for the real thing. It's essentially adding another difficulty setting. I don't even do anything with the settings in emulator when I do use it, so I have no idea what Oyama and the rest of you are even talking about with regards to "slowing things down," but I don't see how doing so in practice would negate scores played legit.
And of course the big question is, if we are having this much trouble just enforcing "don't cheat when you play," and have only recently started to think about making photos a requirement, how in the world would you suggest one enforces what someone does to practice?