In the tripcolor docs this is in a separate Notes section. Do you want to do the same here? On the other hand, if it is discouraged, do you even want to mention it as a possibility?

Since x, y, triangles, Z was a previously documented variant, I don't want to silently undocument it. We either have to stick with the discouraged notice or should go with a proper deprecation. It's not so easy to add notes here, because the docstring is left partial so that tricontour/ tricontourf are able to add additional specific parameters. In general, I think this information is better placed near the call signature. I've moved the info up in tripcolor so that they are consistent.