It used to be that the labs producing peptides. which is no simple task, also lyophilized them. So the process was carried out by people who knew what they were doing, even if not up to pharma standards.
Now they sell bulk peptide inexpensively, and lots of places mix up their own recipe with random excipients, put the liquid into the vials, insert lyophilization stopper, and lyophilize like they're microwaving some popcorn.
Even US sources sell them inexpensively now. Though obviously Alibaba etc sells them for much less:
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juicerville.com
I very much doubt they even sterile filter the solution, which even any homebrewer making gear would do.