How about this thought.
It has been posted many times, there are at least 3 different injectables, that people have discovered. This was close to the beginning of the "vax" program. So say now, they completed the testing, they wanted to do with the 3 variable/control groups. Now they just want the cattle dead and gone. Those that didn't die within a couple months, will now be getting their lethal doses. They can't have them all dying at once. It has to be staggered.
spitballing