Just checked, and NES/SMS/GG emulators exist for GBA, so I'm thinking all non-GBA games seen on the screenshots have been made using those.
Basically, the console only runs GBA games, but can run GB/GBC/NES/SMS/GG if you wrap the roms using the respective tools (Goomba, pocketSMS, pocketNES). So technically, they are not lying, you can run those games.