An encoder shaft can spin continually and wouldn't have a resistance value printed on it (unless there's a coincidence with some other meaning). If it stops short of full rotation it's a potentiometer, and a dual concentric one with detents at that (like some hi-fi volume controls). If it reads 10k resistance with a DMM across the outer pins of each section, then it's a 10k pot and if the centre pin reads a variable resistance to either end pin when you turn the right shaft it's a working pot - rear section is driven by the long spindle shaft.
Are these possabilities?
https://www.banzaimusic.com/Alpha-9mm-Dual-Concentric/...still don't have detents. Digitech may be using it with the detents to detect the resistance at that position and measuring it to find the function you want at that setting.