Hi rrr
Could than be explained by the FBW computers sensing the rate of speed decay, knowing the rate of pitch change available, and anticipating the change in attitude necessary to avoid exceeding aMax?
Possibly, but it could be any number of reasons, and with absolutely zero knowledge of the VFW laws I would rather not speculate.
I would add though that the time history as shown is not IMO a very good response to a step elevator command. It certainly shows an effective limitation to alphamax, but as a response to a demand for maximum lift NOW! it leaves a lot to be desired. Sure it gives alphamax fairly quickly (as it should at 180 kts) but it only stays there for a very short time and that is followed by a very large response reversal and a slow climb up to maximum lift. In fact it takes about 20 seconds to get to a sustained alphamax.