Right, but the only people in that room all know that they are still alive.
Better safe than sorry, maintaining the false narrative at all times so you don't let it slip. Besides, it's not like they're ever going to see them again; they aren't in protective custody, they are, for all intents and purposes unless they themselves reveal that they're still alive, dead. Maintaining that legal fiction is easiest.
Guess the flower thing is a reference to how fallout is removed from the soil
"Aiming to recover the soil for farming, scientists and farmers have tried to find the way how to remove the radiation from the soil. Among various expensive methods, they found the solution for solving the radioactivity problem in the areas with high farming rates. This solution is a sunflower plant, which as the hyper accumulator, has efficient mechanisms for pulling nutrients, water, minerals and certain radioactive isotopes like strontium and cesium from the soil. Sunflower is attractive also because it grows well, produces a lot of biomass quickly, it’s adaptable to a lot of different climates and it doesn’t take a lot of management to grow, compared to some other crops."
"Planting of sunflowers is, for now, the best solution for removing of radioactive isotopes from the soil, but scientists need to find out new farm technologies to achieve better results. Since radioactive isotopes act like plant nutrients, strontium is very similar to calcium and it’s very available to plants, while cesium acts like potassium which is fixed to the soil particles and it can’t be easily removed from the soil."
Very interesting, I hadn't researched that aspect of fallout removal; thank you for prompting me to do so!