This one’s a little complicated to explain in the abstract, so I’ll give you an example: Let’s say I’ve got a table of Students and a table of Classes. The primary key on the Classes table is a number field rather than a single-line text field, the number corresponding to the graduation year. In the Students table, there is a field that is a link to the Classes table, so that each student can be associated with their graduating class. Let’s say we have a student named John Smith who graduated in 2015. The record for student John Smith would have associated class of “2015”, which links to all the properties of class “2015”.
Now, lets say I’m on the Students table and want to filter out all students who graduated before 2014. When I hit Filter while viewing the Students table and chose the Class field (that is, the field that links to the Class table) the filter options I’m given correspond to single-line text (contains, does not contain, is/n’t empty) rather than the data type of the primary key, number. For this purpose, that wouldn’t work very well as I would like to be able to filter students based on class number being greater than or equal to 2014.
I recognize that since you can link to more than one record, you may need additional logical parameters (any vs. all). But I still think it would be useful.