This is also showing up for me too. iMac 21.5" for the MBP 13.3 SPACE GRAY. I literally logged into to Jamf Nation to create a ticket. This is causing some issues with my policies when trying to setup targets for MBP's.
We understand this to be an issue with Apple's DEP API responding with incorrect model information. Once a device enrolls, the inventory should display correctly according to the device response. You can open a case with Jamf (PI-006983), however this is actually a third party product issue tied to a radar with Apple. As such, filing an Apple radar and referencing either rdar://50318529 or rdar://51222311 will ensure Apple hears the feedback.