I haven't read the whole thread as there are already around 400 comments now, but I did see quite a few people say, "MMS is not part of 3G".
Well, you're both right.
Kind of.
MMS predates 3G, for sure. I was working on MMS implementations for GSM and GPRS devices back in the early naughties. I even worked for a start-up who's business model was built around MMS-based apps - all before 3G was launched.
The trouble was it sucked. One of the things we spent a lot of time working on at the start-up was equalising all the differences between different implementations of MMS.
Also, after working at three different companies where I was involved with MMS implementations, I still struggled to actually send the damn things myself! I think I have successfully sent a total of two MMS outside of lab conditions in my life (I'm sure hard core MMS users will laugh at this, but it's true).
And when you did send them they were quirky, limited, awkward things that you realised you never wanted to use if you could help it. Why can't we use email instead? Oh yeah, phones don't support email (well, some did through tricky to use proxies and such)....
The 3G spec incorporated MMS and extended it a little. My involvement there was limited, so I can't go into too much detail but I believe some of the limitations were removed, and possibly the standard was tightened to remove too many implementation differences.
So my guess is that what Apple mean is that they have a complete 3G stack (which I believe was bought in) which includes 3G's MMS standard. They have just added the UI for this release so we can actually use it. But to support it on the 1st gen phone, which is theoretically possible, would require them to implement a whole parallel version of the MMS protocol (probably in-house), to a looser, and more problematic, spec.
So saying that it's a "different radio" is not strictly accurate, but not entirely out either. After all, it just summarises what I have spent a screenful of text explaining in two words