The surnames for Franz and Erika are clearly hyphenated, whereas Frank’s is not.
I looked through all the names for this cemetery and while hyphenated names are not the norm, they are not uncommon.
Wikipedia, as is usual, as a nice article on “Double-Barreled Surnames,” and in the case of Switzerland states:
“In Switzerland double surnames are traditionally written with a hyphen and combine the surnames of a married couple with the husband's surname in first place and the wife's second. This double name is called "alliance name" (German: Allianzname). The first name as such, however, is the official family name, which will be inherited by their legitimate children. So, for example, if Werner Stauffacher is married to Gertrud Baumgarten, both can use the name Stauffacher-Baumgarten. Their children Heinrich and Verena, however, bear only the surname Stauffacher. Prominent bearers of an alliance name are Micheline Calmy-Rey (former Federal Minister for Foreign Affairs), Eveline Widmer-Schlumpf (former Federal Minister for Finance), and Johann Schneider-Ammann (Federal Minister for the Economy). Lately, based on feminist pressure, wives have been permitted by law to place their maiden name before the family name. This double name is written without a hyphen and is borne by the wife only. So, in the example above, the wife's name is Gertrud Baumgarten Stauffacher, while her husband's is Werner Stauffacher. Again, the children's names remain Heinrich and Verena Stauffacher.”