"Mxsmanic" wrote

But the AP aileron deflections do not appear to be small, as it rolls the
aircraft rapidly and smoothly into a coordinated turn. And this is on an
aircraft designed sixty years ago.

Piper, Mooney, and Beechcraft (to name a few) all produced aircraft with
mechanically coupled rudder/aileron systems at one time or another, and may
still do so.

If you're really interested in which aircraft models had them and how they
work I suggest a web search - the info is out there.

BDS