As it was explained at 'Linear Actuators review - Part I', the LA rod tends to freely rotate under drive, if the piston is not fixed.
However the "problem" is that you can't determine exactly how much it will rotate and extend/retract, when the piston is free. It will always depend on factors that affect internal friction conditions, like the inclination at which the LA is operating and others.
Below some videos found at YouTube (thanks Didier for pointing them to me), which illustrate this behavior very clearly despite it looks totally deterministic here.
These also confirm my calculations that a PF XL-Motor should take about 7 seconds to extend/retract a LA without load. Here we observe about 8-9 sec.
As a matter of curiosity, here you can see the the LA bracket adapter for the PF motors, in use. This adapter appears at the Telescopic Handler (8295) set box.