I'm totally just guessing, but possibly they still need training data for the new hardware configuration which they will collect from the newly sold cars. They could pay testers to drive them around for a while to generate that data or just roll it out to the public and crowd source the problem. They deliver less functionality at launch but start generating revenue earlier. Most large car companies don't mind deferring the revenue a little after incurring the initial development costs if it means delivering a complete product, but Tesla is operating on tighter margins than big auto.