GMAT Critical Reasoning (CR) | Re: Frobisher, a sixteenth-century English explorer, had soil

Karishma , can I paraphrase the above highlighted explanation as

Negative E - Gold was added to the soil samples collected by Frobisher before the samples wereexamined.

Now that if gold was added before examination and the examination rightly pointed this out - it clearly shows that the technical method to determine the gold content was not in-accurate ( though the step of fudging sample was morally wrong but that is altogether a different matter)

So negating assumption , destroys the