I think one of the things with mutagens is that they’re really not all that complicated. The blob does the work for you. Discovering them in the first place was probably a bit tough, but the materials are swimming around for a survivor with no regard for safety or consequences.
Remember, scientists frantically trying to craft a super soldier serum probably weren’t okay with “aw, got hollow bones, well, I guess we’ll try a few doses of purifier and go back to the drawing board”. They were trying to create something reproducible. And we have no clear idea exactly what they achieved with their better processes.
Well, the book with the recipes for the Medical Serum are described as having “APPROVED” stamped on the front. So that one had at least entered beta testing.