The handbag situation is, I think, quite an interesting one from a psychological angle.
For most handbag users, after many, many repetitions of the behaviour, it would have become an automatic response to grab their handbag as they get up to leave (from any situation). The bag-grab should have become almost instinctive, without any thought, and consuming very little time. (One might argue also - that handbag users entire motion, or action of getting up to leave, has become integrated with the bag-grab.)
So to ask someone to not do something behaviourly instinctive, to think and make a conscious decision to not respond automatically in an emergency situation, would likely slow them down as they processed the thought and actioned the behaviour change. Additionally, the subject is likely to continue to second guess leaving the handbag behind as they exit (as their brain would be subconsciously pinging them for not bag-grabbing), which would distract and slow them down further during the exit process.
So I would posit that it may be better for a handbag user to waste a few microseconds grabbing their handbag* (as an instinctive behaviour) so that they are then primarily focused on exiting the aircraft - because if they are not primarily focused on exiting the aircraft during an emergency they will actually slow down by seconds (not microseconds).
* when the bag is in easy reach at their feet.