Is there a word that describes a person whose given name and surname each contains but a single syllable?
The best I can think of is to say that their names are disyllabic duonyms, making them disyllabic-duonymic.
Such an answer though is in the realm of fun word games with obscure terms, rather than anything of much use in real English use. Don't say anyone is disyllabic-duonymic, except perhaps as a joke, aimed at a rather nerdy audience.