That's "pretty believable" but it's also complete bullshit. Why do you feel it necessary to comment in an authoritative manner when you don't know what you're talking about? It's literally spreading misinformation.

The relevant technique is called "serial dilution" and it's regularly practiced in intro level chemistry and molecular biology classes. An otherwise untrained undergrad, using only a pipette and a volumetric flask, can consistently and reliably dilute samples to nanogram per liter levels. The error accumulates as some (exceedingly small) percentage of the target value per dilution step so even after 10 or more steps the error will remain well within manageable range.

The issue is not fentanyl having a power level over 9000 or whatever other nonsense. It's people who don't know what they're doing, don't have access to a proper setup, and have no realistic way to implement a proper quality control regime manufacturing pharmaceuticals.

Fentanyl didn't kill all these people. Objectively poor public policy indirectly led to the deaths of those who violated the law just as it did during prohibition.