Currently there’s only one file there that matches this, it’s the OTA file.
Furthermore, the guide suggests installing with TWRP, and TWRP can only install the OTA file.
The other files are named “manual” and need to be installed with dic:fastboot following the manual installation procedure given here for Fairphone OS … https://support.fairphone.com/hc/en-us/articles/207914363.
The “OTA” and “Manual installation” files, despite being labelled “upgrade”, are working for full installs from scratch, they are not only updates or upgrades. The switcher files don’t work for full installs from scratch.
I agree it could and should be made clearer on the page what each file is intended for.
If you really want to go for default state, I suggest doing more …