"GET/displaygroup" does not contain a display

I’m using cms 2.0. 4.
If I don’t specify isDisplaySpecific = 1 in “GET/displaygroup”,
A display that is not a group is not listed.

(So I combine the results of isDisplaySpecific = 0 and 1 to get all the display information.)

Considering the behavior of playlists, layouts and campaign APIs, I think it’s natural to display them together.