Bullrock,
I have heard no reports so far of different backstraps coming with the gun.
However, many (if not all) of the guns ARE packaged with 3 magazines. Some dealers have left all three in the package while some of them are removing one of the three and selling it separately.
Beretta has confused the issue by trying to differentiate between guns destined for LE use vs those for commercial purpose. They say that commercially sold guns should only come with 2 mags. The problem is that many of the "LE" guns are going into the commercial supply chain as LE response has been less than enthusiastic. It seems that Beretta has informally let the dealers know that commercial guns come with 2 mags and LE guns with 3. So, when some dealers get an "LE" package, they take one of the mags out to comply with Beretta's wishes (or to make a little extra) and sell it separately while some just leave it in.
This is, in my opinion, a MAJOR goat rope. As a dealer, you should NEVER open up a factory package and remove items from the package before selling it to a customer. That's just begging for misunderstandings and ill will. Beretta was EXTREMELY foolish to try to differentiate between LE and commercial guns (there's no difference, just their own internal decision) and more foolish to try to impose their internal decision on the dealers when it was bound to cause such confusion and ill will.
You have pricing confusion because no one ever knows if they're getting the 3rd mag or not. You have customer confusion and irritation when they look at their package and see where it says 3 mags but they only have two. You have people who got only 2 talking to those who got all three and trying to figure out what's going on. It's just a mess and it shouldn't have happened the way it did.
The bottom line is that as long as you knew what you were getting and what you were paying, you weren't actually ripped off, but I think that the dealer should have explained the situation to you in good faith.
But I still think that things were handled very badly, and some dealers selling guns with only 2 magazines are making it worse by trying to claim that they HAVEN'T been removing magazines from packages but can't seem to explain how they happen to have UNPACKAGED new factory PX-4 magazines for sale...