Sangheili Major: "Brute ships. Staggered line! Shipmaster, they outnumber us, three-to-one!"
Rtas 'Vadum: "Then it is an even fight. All Cruisers, fire at will! Burn their mongrel hides!"
There is no way.
You can play Noble Six as a female, that would be quite ridiculous if you could play the Master Chief as a woman.
The male voice is also different, the Master Chief was in an entirely different location.
There are more reasons that have been previously posted.
Too many facts go against this theory, thus deeming it untrue.
Not to mention its quite an odd theory to come up with, in all honesty, having read the books or not. I would assume it would just be known that they are not the same person.