I tested the issue with the following devices:

• FP2 - /e/ OS 0.7-2019080919577 - English Interface
• S7 - eel 0.7-2019062814891 (bought it in the /e/-webshop) - German Interface (also eel 0.7-20190820896)

If I search in the config (germ.: Einstellungen) for "reset" (germ.:zurücksetzen), I get the result "Backup & Reset" and "Factory data reset", but after choosing one of the both results, I'm in an empty "backup & Reset"-menu (see attachment)

So I'm not able to perform a reset on my phones (only via TWRP)