ECC RAM is basically "server grade" because desktops don't use it. That's all. Now if some company is trying to brand something as "for Mac" or something, that's an issue you'd have to ask the marketing department of the given company.
Do keep in mind that to use ECC RAM you must have a CPU and motherboard chipset that supports ECC RAM. So unless your machine has a server chipset (C200, C202, etc.) then you aren't going to get ECC just by putting in ECC RAM.