I did google and it is very confusing.
Seems flying will extend all miles for another 2 yrs. But not sure it will also convert all miles into flight miles. I did fly air France back in 2019 and don't know if that converted all my Amex transferred miles to flight miles.
Some people said transferring ultimate reward points extend all their miles including flight and non-flight miles. Others said it only extend the non-flight miles. The problem is how to know what are flight and what are non-flight. Apparently, using miles does not qualify as activity to keep miles alive.