That's a curiously coincidental date. It's the first day of Summer. I'm guessing someone took a little license with a broader "this Summer" target and tried to milk an exact date from it.All EV-certified dealers will have a couple demos sometime after production begins. Currently "Job 1" is scheduled for June 20, 2020.
My understanding (from talking with my dealer) is that the initial production will be a small number of demos and then First Edition, followed by Premium trim. The dealers will get only a couple demos, but people can see and drive them before the first reserved production units are shipped.