I do think Jones is fairly perceptive and correct on the fact that a lot of Corbyn supporters seem to be getting wrapped up in their own base on social media, forgetting that to actually have a chance of winning anything, they need to appeal to precisely the sort of demographic who have nothing to do with social media.
I don't think this is anything that's exclusive to Corbyn, though. Up in Scotland, social media was dominated by Yes voters during the referendum, but it's still older people who tip the balance to Scotland just supporting a No vote.
Likewise, it's something that's already existed within Labour, and will continue to do so. I'd suspect Miliband had many more supporters online than Cameron in 2015 - I'd also suspect that plenty of them will now be supporting Smith. Should be come to power, I expect Smith's Labour will face a similar problem to Corbyn's - appealing mostly to younger, online voters who use social media (except the Corbyn or nothing ones), but struggling to gain a wider appeal among a Tory party which largely dominate the media at the moment. If Jones or others expect this social media problem to be in any way rectified by a new leader's appointment, I think they'll be very, very surprised.
The calling it "brave" stuff is also a bit silly and ridiculously exaggerated though; the exact sort of exaggeration Smith's supporters would laugh at Corbyn fans for whenever they talk about being under siege by the media or the rest of the party.