I wondered as of recently, why weight gain is not called a tardive side effect. I cannot shed weight and my personal trainer who has had medical training immediately spotted that my belly fat looks and feels much different - tougher - than post baby belly fat, so, she guessed, it must be from psych drugs. I assured her that after each of three kids, I lost weight without trying. She said that the drugs are still there on a cellular level. I don't know what that means. Her point was that such fat is much harder to melt.

I know a lot of people on here similarly struggling. Enough to qualify this side effect as tardive.
New Injectable Antipsychotics May Be No Better Than Older Meds | Psych Central News

This article finally talks of weight gain and involuntary movements as two types of persistent adverse effects. Involuntary movements are one example of tardive dyskinesia. In essence, they are saying that weight gain is often tardive.

Now we just need it printed in red ink on top of the list of possible Side effects:

- weight gain, which is likely to not go away even if the medication is discontinued