First, there isn't a "default.zip" for Main Menu in HyperSpin. The Main Menu themes are the correct proper HyperSpin/RocketLauncher names like "Super Nintendo Entertainment System.zip" Second, HyperSpin Main Menu themes are only shown when you enter the AttractMode "Displays" menu. Third, "nintendo snes" isn't the correct naming convention for HyperSpin... it should be "Super Nintendo Entertainment System". Forth, your AttractMode "Display" names need to match the correct proper HyperSpin/RocketLauncher names.
To get it working you want to use these paths and files names and make sure that your AttractMode "Display" names match the system names that HyperSpin is using.
Main Menu (a.k.a. Displays menu)
./attract/layouts/Media/Main Menu/Themes/Super Nintendo Entertainment System.zip
System/Emulator
./attract/layouts/Media/Super Nintendo Entertainment System/Themes/Default.zip