No, I meant this
Basically they want your money first and then deny you boarding at the gate. And even if you do play their game, yet show up late (say due to a late connection) your "extra seat" may not be next to you anyhow.
It's best to buy 134 seats, just to make sure!
A "person of size" should be accomodated just as any other passenger would be once they are on the flight. If a minor is found in an exit row, for example, passengers are asked to move.
If a passengers size makes them a hazard to evacuating the aircraft, perhaps they really shouldn't be allowed to fly at all if their BandC seats put passenger in A at risk. That's a valid excuse. But selling somebody a seat without telling them upfront that they may actually need to buy 2 is deceptive.