Sasha has an excellent summary of recent analysis on the supercharger issue:
more helpfully, from yahoo news:
Which sounds quite plausible to me. Sounds more like elon being dissastisfied with location selection or size of sites, or speed of rollout. Also may have an eye on megacharger rollout, and know the team needs to be more ambitious in terms of grid connections.
Not at all unusual for grid connections to take years for power draws in the megacharger range. Everyone's grid is overloaded. Even if we are 18 months away from production line tesla semi's, they need to get their act together on megacharger sites fairly quickly.