I believe it does provide credibility to @ggr and @Words of HABIT theory.
It really does not. As far as I can tell, insideevs uses various data sources to get pretty good monthly estimates, generally coming quite close to Tesla's reported sales, and trues up its numbers as needed. I suppose it is possible that they are a bunch of lying, Tesla-hating scumbags, who are trying to destroy Elon Musk by claiming his US sales are somewhat concentrated in the last month of the quarter. But really, isn't that pretty far-fetched? They are insideevs.com, after all. Why would they want to harm Tesla? If they did want to harm Tesla, they could do something more effective than suggesting their sales are a few weeks later than they truly are.
The insideevs people seem like decent folks, being completely transparent about their methods, its weaknesses, and it's record of accuracy. Here's what they say about it:
"Tesla does not give out exact monthly sales (
apparently because the public can’t handle the concept of regional allocations and delivery lead times). For this reason, we never know
for sure what the monthly numbers total up to until Tesla’s quarterly (or annual) updates add more clarity. However, we do our best to keep our finger on the pulse of what’s happening.
To come to an estimated monthly number, we
don’t simply take the quarterly estimate given by Tesla and
divide it by 3 and hope it all works out. This is surely not how it works in the real world. We simply report from the data we accumulate ourselves, including first-hand accounts available from the factory and from the community itself, and the number is what it is (see below).
Revisions/disclaimer to the accuracy of prior estimates: The
2016Model S chart has been adjusted (via
U.S. Q3 data leaked directly from Tesla) by
469 units in Q3, and
525 units in Q4. The
2015 chart was adjusted (one time) by
498 units to compensate for confirmed full-year numbers. The
2014 sales chart was adjusted (one time – again after the end of the full year of estimates)
611 units to compensate for full-year numbers. While past success is no guarantee of future results,
InsideEVs is quite proud of its sales tracking for the Model S over the years.
That being said, we
only estimate this number because Tesla does not, and to not put a number on Model S sales would be to paint an even more inaccurate overall picture of EV sales. Despite our fairly accurate track record, we’re not analysts or portfolio managers and we don’t own any positions in Tesla the company."