“How did Airbus avoid the installation of a Shaker/Pusher? … this decision, to omit the stick shakers?”
The certification regulations do not require a shaker or stick pusher – or any other stall recovery ‘device’ if the aircraft meets the stalling criteria.
IMHO this would have been evaluated in all control law configurations, and thus we might assume, and as indicated by some incidents, that the A 330 has conventional stalling characteristics and does not require any special assistance or technique for stall identification or recovery.
A stick pusher is not installed to prevent a stall, it is a recovery device.