Folders containing files that need to be uploaded or downloaded in a Synchronize Folders action are not displayed with an arrow next to them. This prevents the quick determination of which folders have files that will be up/downloaded, and forces the searching of every folder.
The Climate_Change folder in attached screenshot has no arrow, but does have files within it with arrows. Note that the subfolder, Climate_Change_Assets, also has no arrow.
It appears that the arrow is displayed only when the entire folder itself needs to be uploaded or downloaded. While logical, this choice isn't all that helpful.
Before you open the folder it is not known what files it contains and what the appropriate action will be. If you have choosen to Upload only (as in the above screenshot), there is no download action anyway but only uploads for remote files missing or out of date.