The official MkDocs page, states that the Read The Docs platform accept only the MkDocs readthedocs theme.

To benefit from all of the features offered by Read the Docs, you will need to use the Read the Docs theme which ships with MkDocs. The various themes which may be referenced in Read the Docs' documentation are Sphinx specific themes and will not work with MkDocs.

Fortunately Read The Docs is more tolerant, though I do not know how much. I can say for sure that it accepts the Material theme, since I am deploying the documentation of MkDocs-Macros on Read theDocs.

Would it be a good idea to change the wording?

Also it might be a good idea to liaise with Read the Docs team to update their own doc, so that they list the MkDocs themes they support?