They had seats. Did you read the article?
No they didn't. The adults sat on two folding crew seats for take-off and landing and then had to move to the floor as the crew space was needed for trolleys. I think that the question is, how long would it have taken them to get back to the crew seats (presumably now blocked by trolleys) in the event of turbulence?
They could be in their seats at any time excluding removing the trolleys
Why then were they asked to sit on the floor for the entire flight (apart from take-off and landing)?