After reaching out to the team, @R.Good came thru (as usual), having tested this in the past and confirmed your findings with some added information.
It appears as though when the Floodlight is set to activate on both PIR and camera motion, there is a 10 minute reset period after the rule turns them off. This does not appear to be the case if only one of the activation methods is set to activate.
See these posts that explain the tests and results: