I'm guessing his point is that "4 GB" is a big problem on a phone.
There are hundreds of millions of phones running Java today, what does that tell you?
It's not if you meet one of these typical "don't do any premature optimisations (even in the design phase of my data structures), because some important CS person said so"-designs. There's all too many programmers who think they should never have to care about hardware anymore.