Evidence: stored Eq "View"; SharePoint read the query back as "<Where><Eq><FieldRef Name=\"Evt\" /><Value Type=\"Text\">View</Value></Eq></Where>". OPEN <sharepoint-url> dbmlsp multi value probe/Probe membership.aspx and confirm it lists exactly R1 and R2. A view that lists everything, or nothing, means the predicate does not survive storage and the condition grammar must refuse it however well GetItems behaved.