Hi,
That statement is made in all Intel documents, the only thing that is varying is the total amount of memory.
To my understanding, this is a "problem" only when you have the maximum amount of supported memory, and even then, it can be overcomed through BIOS.
Funny thing is, I previously had an 975XBX2, which states the exact same thing, but which didn't have this problem, and I sincerely doubt this "legacy" thing is still an issue for today's chipsets and BIOS.