On the floor at their feet or under the seat in front of them?
No one is allowed to have items at your feet for take off or landing. Should there be a need to exit quickly no one should have to climb over "stuff". If the FA was asking them to "tuck them in tight" I'm assuming she was referring to under the seat in front of them.
If you could not see the location of the item(s) she was referring to, maybe you just assumed they were at the passengers feet when they were not.