yes it is true link below for more info. 3G does not have the compatibility to play online games that are not turn based. that is just how 3G works.
Want a option to buy avatar's on the ps vita's psn store. Then vote on the link by copying it to your web browser.
That's because 3g is a high latency, low bandwidth transmission medium. Meaning it's slow in both directions. It would be ok for turn based games (ie: chess) but anything in real time would not only suck (and waste devs times trying to unsuck it) but it'd waste what little bandwidth you get per month.
It's only going to be used for small data, ie: twitter, web browsing, messaging