The difference is that placebo is an objectively measureable benefit, regardless of whether they report being better or not.

Misreporting is a reported benefit, regardless lf whether they are objectively measureably better or not.

E.g. joint inflammation could be an example. Measurable reduction in inflammation with a calipers could be induced by placebo, even if patient doesn't report feeling better. But reporting feeling better may not come with any measured reduction in swelling.

Placebo is not (just) in the mind, it is in the entire body!

I acknowledge it is less clear-cut in mental health, but I just wanted to answer the general question outside of this specific context.