Correct me if I'm wrong, but as I understood it, 3G is strictly for data, while 1X is strictly for voice. If you've ever watched closely on your 3G VZW phone, when you make a call it switches to 1X. The reason that voice and data didn't come simultaneously was the fact that 3G and 1X used two different antennas within the phone.
However, with LTE, voice AND data can come through at the same time while only being connected through the 4G LTE antenna. Also, I know I read somewhere that new VZW 3G phones will do simultaneous voice and data albeit the data will be a joke, apparently the reasoning was atleast partially to keep new iPhone uses happy because of all the hype AT&T always made about it talking and surfing.
The TB in fact is supposed to have simultaneous voice and data over 3G (see attachment). However, as you mentioned it probably won't be very good. I think this is both unfortunate and a bit sneaky by VZW. I was fully expecting simultaneous voice and date in NON 4G areas. Oh well... However, its 4G is strictly data only for now. VZW is talking about VoLTE and have tested it. I think it will require a hardware change not available on the TB (could be software only, but that would be highly unlikely IMO). Either way VoLTE is coming to their 4G LTE network. Thus the simultaneous voice and data they are talking about is really 4G LTE for data and 3G (1X) for voice.
I'm not currently on Verizon but I think you are correct about voice and data using different standards.
3G is a general term, both voice and data travel over a 3G network.
"1X" = CDMA2000 1X, which is technically a 3rd generation standard, 3G. It can be used or both voice and data but probably VZW only uses it for voice.
"3G" = CDMA2000 EV-DO (or EV), typically used for broadband data (DO = data only).
I do not think VZWs "3G" and "1X" require different antennas. Both are in the 700 Mhz band. But perhaps it is 2 identical ones, one for data, one for voice.