It doesn't seem to be a commonly understood limitation of the type of testing we have access to.
The standard in science, pharma, and regulatory agencies requires multiple methods of testing peptide drugs for contamination since they all have "blind spots" that need to be compensated for.
The physical particulates in cheap Chinese vials not certified to meet USP (the standards setting organization the FDA follows) particulate standards alone warrants filtering.
Injected glass and rubber particulates have been found lodged in many organs during autopsies. They create "micro embolisms" and/or chronic inflammation. With no natural means for glass or rubber to be broken down or removed, they accumulate with each injection.
View attachment 6200