I'm gonna try to be as polite as I can with this response...
I'm sorry, but the story you theorized just makes me so damn frustrated. I mean, where did you get it from??
My own head. I don't know if any of this actually happened, because to get the correct answer, I'd have to be an employee at Universal. Sadly, this is not the case. I don't know why you're still so bothered by it.
And why would they be tired of a perfectly good voice??
I have no idea if it was them or not who may have specifically said they were "tired" of it; it might've been Bennett himself, for all I care. Maybe he just wanted to experiment further with the voice or something. Again, this is only a theory that I wrote over a year ago, so who knows what might've actually happened.
And why would they call Bennett "sir"?
Umm...because the staff considered him the king of perfecting a role?

For all I know, the kid who played Littlefoot could've been called "Your Majesty" or something!

:
And why didn't you consider that some people love Petrie's voice of movies 1-4??
Um, excuse me? I am very much aware of the fact that a lot may prefer the original voice over the newer one; in fact, my friend Jrd89 said a while back that that's the Petrie that he prefers. I'd actually watched some of the LBT films years back (including the first one), but I'd totally forgotten about him until I was re-introduced, so I'm not even sure which one I heard first. That said, I like that voice too (it was the Petrie
I was re-introduced to); however, it is simply a matter of preference over what I like better. And who knows? Maybe it'll change within the next year or so or even further down the road. With that being said, it is simply an opinion that I am entitled to. You are also entitled to
your own opinion, just like everyone else, so I have no idea why you're the one to judge mine.
Btw, what is this about his voice not sounding deep in 3 due to recording timing??
I'll sum all of what I noticed up in a nutshell for the first few sequels regarding his voice.
LBT 2: Same or very similar qualities as Will Ryan throughout.
LBT 3: You have to pay close attention if you want to get analytical here. Some of his lines were spoken using the same voice as used in LBT II ("Sorry! Me no know my own strength.") while others ("What that? It sound like monster!") were spoken using his higher, squeakier voice he obtains now. Both appear on and off throughtout
LBT 4: See LBT 2.
In addition, I actually noticed in LBT 3 that the other kids doing the rest of the gang appeared to be getting a bit older, as I can tell by their voices in that one. This is not apparent in LBT 4, hence my theory that LBT 2 and 4 were recorded first (maybe at the same time even) before LBT 3. I believe I read in a source once that all three of them were being simultaneously produced at the time, and with all reasons given, I believe that LBT 3 was the last of the trio recorded.
Hopefully I summed everything up.