I was going off of whether the title was/is widely considered to be and recognised as monarchical, which excludes Shogun. Requiring the entries to conform to that definition of "monarch" would also exclude elected monarchs and constitutional monarchs, which I do not think should be excluded.
On further thought you're probably right, though it might have been better to make it clearer beforehand. Since actual power was held by the shogun, and it was hereditary, people can easily make the mistake.