I think it essentially dictates that whether or not the list view can be generated via an SOQL.
If you run this query in console
SELECT Id, NamespacePrefix, Name, DeveloperName, IsSoqlCompatible, SobjectType
ORDER BY IsSoqlCompatible
You will see that couple of object have
IsSoqlCompatible as false, objects like Apex classes, lightning bundles, Visual Flow, users.
For me, some of the list views in
USER objects were showing as true and some as false. So I picked the one which said false and went through each field in display and filter condition. I noticed that if the list view contains a field which is from a separate table but has a one to one relationship with
User is included, the
IsSoqlCompatible parameter is false.
As soon as I remove those fields, the parameter becomes true. In the case of
USER, the fields were Identity verification fields like
User Verified Email/Phone.
Salesforce has ability to create list view spanning multiple objects which are shown as to be a single object on the UI.
These list view cannot be generated via SOQL so the parameter
IsSoqlCompatible is false for them.