Tesla committed to publishing delivery numbers within three days of the end of quarter. They are just keeping with their commitment, not trying to bury this news by releasing it on a holiday weekend.
FWIW, it published Q1 numbers on April 4th...which would be 4 days after the end of Q1. April 4th was a Monday. I don't think too many people would critique them for waiting until the 5th of July, the Tuesday after a huge U.S. holiday, to publish news:
http://ir.tesla.com/releasedetail.cfm?releaseid=963460