In general Adam Jonas is quite positive about Tesla. He just thinks that based on Tesla's past performance in bringing new models to market that the Model 3 will not go into production when Elon has stated it will. But the situation is not as simple as Elon saying that Model 3 production will start on July 1, 2017 (which he has clearly said is his target). This well written article provides some valuable context Tesla Model 3 again predicted to be late as WSJ piles up on ‘Tesla/Elon Musk are always late’ narrativeJonas? Why does anyone care what this pretentious d-bag thinks? I certainly don't.
Jonas has also been accused of hyping Tesla just before the company planned to raise more cash. See http://www.nytimes.com/2015/08/29/opinion/joe-nocera-the-tesla-cheerleader.html
I don't know what goes in in Jonas's head. But he is just one opinion among many.