The author doesn't use an analogy. An analogy would involve pointing to similarities between two different things to conclude that they share another similarity. The author's argument is about human behavior directly, not about something like human behavior. The hypothetical scenario (imagining we had a complete physical account) isn't an analogy. It's a thought experiment about the very thing the argument is about.

The author's "evidence" is the claim that even a complete physical account of a human action wouldn't give us true comprehension. But the only way to accept this claim is to already believe that understanding human behavior requires looking beyond the physical, which is the conclusion. The premise just restates the conclusion in the form of a hypothetical scenario. Nobody who's open to the idea that that physical information is sufficient to understand behavior would accept the premise, because the premise assumes that physical information isn't sufficient.

The author isn't saying "no one has proven physical accounts are enough to explain human behavior, so they must not be enough." The flaw isn't that the author is pointing to a lack of evidence. It's that the author's premise just restates the conclusion.

An argument doesn't need to disclose the speaker's awareness of potential counterevidence. Imagine if you try to apply this standard to other arguments: every argument would then be "flawed" for not mentioning whether the speaker knows of counterevidence. That's not a logical flaw. The real problem with this argument is the circular relationship between the premise and conclusion, not the author's failure to mention counterevidence.

The author asks us to "suppose" we had a complete scientific account. This is a hypothetical, not a claim that science actually can provide such an account. We’re just considering this hypothetical for the sake of following a line of reasoning.