They can't. It's statistically impossible. Even operating theaters and clean rooms can't keep every trace bit of dirt or bacteria out. All anyone tries to do is reduce the incidence to below a meaningful threshold.
If the requirement is: either eliminate every last molecule of every offending substance, or use a label that the offending substance may appear in trace amounts... well, everyone is going to opt for the label.
Nice attempt to straw-man though.
"Ignore the stated argument, discuss my weaker mischaracterization of it instead."
Spirit of that previous parent message was that “never ever contaminated” is not a realistic option.
Yes op stretched that to molecules, but exactly same argument applies to seeds.
I guess you forbid any kind of hyperbole in 50m radius.
In restaurants, little pieces from the metal pot scrubbing pads tend to be a constant problem. But this represents a cost choice: more expensive scrubbing solutions are available.