I am not sure on the math of the 4 PDKs, but a minimum of 2. I agree this validates that it is real and it is happening.
Slide 27 of the Sequire virtual presentation in my view provides the year-end update unless something additional occurs, and I have no doubt there could be added progress as they mention they are meeting daily with foundries, and have already received back prototype devices that are under evaluation - and that the PDKs have been delivered and are in use by the foundries.
Personally, when I review slide 27, I am absolutely happy with the status given on that slide and it fits well with my investment horizon.