This is a really dangerous and misleading way to look at bipolar. The disease proper of bipolar disorder is progressive and degenerative. This progression is accompanied by structural changes in the brain [1] as well as biological changes in the body [2]. If someone had the syndromes of manic or depressed symptoms in response to a medication, that does not prove either way that the person actually has the progressive…
This is also not entirely true. It may spontaneously resolve itself in many cases[0]. I suspect that we've grouped a number of different disorders under the label "bipolar" because they all manifest with similar symptoms.
[0] https://www.sciencedaily.com/releases/2009/09/090929141530.h...