A collection field is used on a page while the collection data item is kept on the Main Page.
When you go to the Main Page and right-click -> Find References, what would you expect to be informed? That the data item is referred to in the Main Page AND in that page in which you are using its field right? Wrong... the only reference it has is on the Main Page.
Check screenshots for a better idea.
I know that just below the data item, in the "Find References" window, you can find its fields references on those said pages, but, in my opinion, if there are 3 references to one field in one page, and another 3 references to another field in a different page, for the whole collection there should be at least 6 references, 3 in each page, being the sum of all the fields references across the code.
The idea here then would be to have references tell you where a collection is used, disregard if it is the whole collection or a field from it.