The way I see it, Mima's orbs seem to require some serious firepower
You mean Marisa's. :V
Well, the way I see it here is that there are bugs, and ZUN decides they're ok and puts them into the readme. However, I doubt most of these are intentional, but since (for the most part) they aren't game breaking, he leaves them in there and makes it a feature. I think the rapid fire from SoEW was an oversight, but since it didn't really change the game much, he didn't think it was worth his trouble to fix. Only after did he have each time you press the shot key, you shoot a limited amount of amulets/whatever, and can't shoot while that's happening. The overpowered MarisaB laser in MoF he knows about, but doesn't feel like fixing it. (he put a decimal in the wrong spot) Luckily, vsync patches fix this. Is this really not the same scenario? Only thing he did differently was put one in a readme and the other not. And being a coder myself, I can see how both of these are quirks in the code, when you think about the coding process.
Also, on the topic of bugs, I've also found myself to have loaded up MoF with the graphics all messed up before. It happens very rarely. (think I've had it happen 3 or 4 times ever, and have a recording of one, right before the game crashed)