The information on Boeing aligns with what I had heard and seen. In previous years when Ryanair parked up aircraft in the winter, they would always rotate them into service every three days to ensure they were not classed as "stored".
Picking up on Racedo's point, I heard (albeit third hand) that one of Ryanair's challenges when this virus starts to wind down will be recovering their fleet from Italy. Most of those aircraft have been left for some considerable time now and will all require an "A Check" to return them to service. Only a few hours work but logistically will require an engineer to go to each of the aircraft whereas normally, the aircraft would go to an engineering line station for the check.
Hopefully there will be a Boeing engineer along in a moment to confirm or deny that!!