Hi Smilin Ed,
as I understand it, letting go with this airplane wouldn't be enough because the THS would have trimmed in the new attitude and you would continue at that attitude rather than go back to the previously trimmed speed.
Correct.
AB ALT LAW is a very peculiar manual flight mode. It has a mixture of Roll Direct (conventional aileron behaviour) and auto-trimmed pitch stable mode.
They require different ways to fly them satisfactorily. The ailerons would require constant adjustment, but the pitch only needs a nudge and then let go (else the input gets continuously integrated).
I don't understand why it was deemed necessary to design such an awkward combination.