That seems to me to be a more reasonable theory, if we accept the 2004 Editions as superceding all other editions of the movies (which seems to be what Lucas wants), that Boba was so obsessed with living up to his father's legacy that he imitated him down to the accent. He could have spent a lot of time with journals, videos, tapes, etc. of his dad's voice.
That scene in AOTC where he lifts his father's helmet to his head could then take on an even deeper meaning. It's like he's trying to channel Jango's soul or something.