It is not clearly described in the Airbus documentation, but there are instances where AP is available in alternate law, and then the bus will NOT go into direct law upon landing gear extension, but when you disconnect the AP.
This is confusing to lots of pilots, as the AP in most cases disconnect when the aircraft degrades to altn. law (with the resulting direct law upon L/G extension).
Summary: IF AP is available and engaged in altn.law, then degradation to direct law occurs with AP disconnect i.s.o. L/G down.
This is confirmed in the sim (A320 neo) and confirmed by Airbus (upon query from our fleet office).
Rgds,