I agree that the names should match, I have extracted this from a larger library I plan to release once the Due is here, so artifacts have crept in. Also I assume you do already know 'byte' is simply an alias for uint8_t.
And as far as sizing the types, its done in compile time, and I don't believe your method is any more intuitive. I have my own style of writing expressions, I think it is more of a personal preference thing.
I'll edit the code in a sec, another artifact... done.
b_Data cannot be private.
Original code is fixed now.
Oh and I'm using the Arduino IDE, nothing special ( not relevant now as it was my code error ), thanks for the find.