"Used" is a word with a very broad definition. It doesn't just mean "run as primary operating system," it could also mean "capable of reading any of the bits of," or "looked at metadata of." The interpretation of "at the same time" is also rather flexible.

I'm not saying Apple will hunt you down and sue you (to paraphrase Jon Stewart). I'm saying, unless you're a lawyer, and you have another lawyer representing you, it's best for us non-lawyers not to think we understand legalese.