... which the OP has already started doing based on the prior shop's recommendation .. no.. affirmative statement that the PCM was failing. Possible that it was, along with a transmission issue.
But I second your opinion, the dealership technicians are going to be the best trained and experienced in this scenario.
So since the shop said replace PCM and it'll fix it, and it didn't... are they paying for it now?
Also, disconnecting the terminals does not reset or clear anything (permanently). Just like shutting the power off and unplugging your computer does not clear it all out of any data, neither does disconnecting power to the vehicle. It'll delay the MIL (malfunction illumination light) aka Check Engine Light from coming back on for a bit.. but once the PCM and various sensors and modules report back that there is a problem, it'll just come back on. You need an actual diagnostic scanner/coed reader to at the very least clear all the faults from the system.
But again, if the issue has not been corrected, after enough time, usually so many key cycles or drive time/mileage, the light will come back to indicate you still have an issue.
You need to re-read the fault codes now that you have that expensive, shiny new PCM in there.. see what DTC's show up and if one of them is still that trans code, P0706. If so, transmission shop/dealer shop to check those clutch values.