Is Apple's Device Enrollment Program (DEP) tied into the OSX Installer, Hard Drive or Machine? My case is I bought a macbook off eBay, reformated the SSD inside it to High Sierra then transfered the SSD to an older Macbook and that's when I started getting the DEP notifications. The older Macbook previously never had the notifications.
So my guess is the DEP either came from the OSX installer I used or the SSD?
DEP follows the machine, not the installer or drive.
Apple doesn’t have a neat article for this like it does for iPhone or Apple Watch.

https://support.apple.com/en-us/HT201365
https://support.apple.com/en-us/HT208855