We raised wheat seed to use for planting. I bought foundation seed and produced Registered seed for my crop 2 years out. Then planted registered seed and produced certified seed.
We have a seed cleaning and treating plant. So each year we carefully clean the seed drills, the combine (we own one, don’t rely on custom harvesters for our planting seed crop at any stage), and the seed cleaner. Normally we only grow a single variety at a time to make the clean up complete. Including the seed cleaner itself.
Then there are the purity and germ lab testing that is done for each plot that is required in order for them to sell me certified seed tags. (and registered)
I know about planting seed purity issues.
Don’t recall saying anything about seed purity, but ok.