The body will develop a tolerance (or the reverse, a sensitization reaction) to just about any substance that's taken regularly due to homeostasis. However, so long as you're taking a dose that nudges some physiologic signal/need in the right direction, your body's response to the substance will be minimal.
I'd be surprised if you can find anything this isn't true for.
A lack of studies on what the tolerance looks like for a particular substance does not imply that tolerance does not form.
In the case of melatonin: It's almost universally true that your sleep quality is worse than it was before once you stop taking it (for a few days at least). That's an indication that your body's equilibrium has changed from habitual use.
You're right! Edited the post...thanks for pointing this out was actually a mistake on my part the article was about incorrect dosage which was the point I wanted to make.