Tesla tends to be optimistic on software schedules - a trait that isn't uncommon for software projects, especially when they are trying to deliver software on very aggressive schedules.
At the time AP 2.0 hardware was released to production, they evidently thought they were close enough to justify a December target for EAP to reach AP 1.0 capability.
As someone who's been responsible for major software projects, it's not surprising this is taking longer than they thought. They likely tested the new hardware with prototype software - and thought it worked well enough to justify the aggressive schedule. But prototype software usually makes some simplifying assumptions, in order to get the prototype up and running quickly - and the extra details needed to make a commercial release can take longer than expected.
Tesla could have been more conservative with the projected date for achieving AP 1 parity with the AP 2 software. In October, if they said it might take 6 to 9 months to achieve AP 1 parity, that probably wouldn't have impacted Tesla sales significantly. We still would have placed our S 100D order on January 20 - and would still complete our purchase (if/when the 100Ds are released for sale), even if the software wasn't working completely with the new AP 2 hardware.
I agree with the comment above, our S 100D purchase is for the long haul - we plan to keep the car for at least 80-100K miles, and if we have to wait a few months to get EAP working reasonably well - that's OK, because the new hardware has the potential to support FSD down the road (even if it takes longer than Tesla thinks they can do it).
