I was on two flights earlier this year where the attendants weren't given seats for takeoff and landing. In the first case the attendant squatted and braced himself in the aisle next to the last row (where I was seated). I wasn't quite sure what was happening, but it was weird.
The next flight where this happened, the older attendant straight up told two passengers ticketed to seats in the last row to get the fuck off the plane and back into the terminal. She was pissed. I felt for the guys because they had boarding passes with seat assignments. Not their fault. (They were eventually seated elsewhere).
I was also assigned to that row so I asked her what was going on. She said that where an attendant seat isn't available they're supposed to reserve seats in the last row for staff. But they're overbooking all flights so aggressively that they're assigning those seats to customers.
I hope they get what they need. I'm a frequent traveler so I selfishly hope it doesn't come to disruptions, but I'm willing to live with sending angry emails to airlines.