This is likely based on what emulator they are using. If it is a version of VICE then the keyboard layout would be according to how VICE is set up.
There is no official statement about which emulator is being used but I would lean on VICE being on the short-list due to certain features that has been indicated is in VICE but some of the other C64 emulators do not have. It is possible that it is VICE with a custom front-end. Of course the front end can set things up in a manner that makes access to certain features more cumbersome. There is a little difference in the emulator's internal menu system between versions on different platforms but they all should all have access to such configurations.
In my opinion, I lean on VICE being one of the likely possible emulators. I am not so sure about other C64 emulators.