Keep in mind that any cars built in this test phase won't reach consumers since they will be built to test the production line. It's also possible that February 20 is a target date that could be missed – something of which Tesla has a history. Plus, as Reuters points out, some final design changes or supplier issues that Tesla can't directly control could delay test production.
However, it's also not completely unbelievable that Tesla could be at this point in Model 3 development. It has begun mass production of the battery that will be featured in the Model 3 at the Gigafactory. And if everything went according to plan, it should have had the design for the Model 3 nailed down several months ago, barring any final design changes. Regardless, we will likely know whether Tesla starts production in a couple of weeks.