As part of the Defect fix DE51973 some changes were done to the code.
Please see below for further details on the defect:
https://knowledge.broadcom.com/external/article?articleId=140632On a release higher than 15.7.1.1 and 15.8, the (new)Tasks, Assignments and Staff modules now show data in hours or FTE.
Note that Days in not a concept enabled on the Modern UX.
However, the legacy Tasks module (now renamed as Tasks Lists) and the Project Details still show the numbers in Days because those are dependent on the general system settings.
The concept of Days is targeted to be introduced in 15.8.1 (expected June 2020)
Once this is live, then all Modern UX pages will have the capability of switching data from Hours to Days and the other way round.