I agree. There is no evidence at all that either pilot was even aware of such a thing as a tailplane stall. Odds are very, very low that they mutually, instantaneously, and with no discussion came to the (incorrect) conclusion that they had a tailplane stall, and then independently attempted to remedy that without informing each other.

Anybody who was smart enough to do all that would also have been smart enough to...

- Check airspeed
- Realize that the other pilot would not automatically reach the tailplane stall conclusion.
- Inform the other pilot what they were thinking and doing.

Ultimately we will never know, but the odds are pretty low based on circfumstantial evidence.

I suspect that...

Renslow fell back on his sim training initially (hold altitude) and then panicked and froze when he lost attitude control.

Shaw reacted without thinking. Something bad happened when she lowered the flaps, so she quickly raised them...a reactive and subconscious effort to undo whatever she had done.

In a crew environment, anyone who is savvy enough to think things through and reach conclusions would communicate with the other pilot. I have a very wide range of operational experience in aviation and other high-risk endeavors, and professional operators in a team environment always communicate. Even if they have to react instantaneously, they always let you know what they did. That's the surest sign on a non-hacker at the entry level...somebody who freezes and stops communicating.