The user is unable to undo the editing of the enum description. The output log and undo history would confirm that the undo was carried out, however it did not do anything in reality.
Resetting the description to default would however fixes this, enabling the user to undo edit of the description.
Result - "Testing" remain as the description
Expected - Description becomes empty
Resetting to default fixes the undo edit:
Result - User will now be able to undo from "Continue Testing" to "Testing"
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-82791 in the post.