Previously, the default query was only Frequency:, which has a chance of selecting unwanted note types (since it will query all notes that have an empty Frequency field regardless of note type). The new query is now Expression:* Frequency:, which searches for any note that has an Expression field, and an empty Frequency field. Although this still bears the risk of selecting unwanted note types, the unwanted note types must have both fields present + an empty Frequency field, which is considerably rarer than just having an empty Frequency field.
Previously, the default query was only
Frequency:, which has a chance of selecting unwanted note types (since it will query all notes that have an emptyFrequencyfield regardless of note type). The new query is nowExpression:* Frequency:, which searches for any note that has anExpressionfield, and an emptyFrequencyfield. Although this still bears the risk of selecting unwanted note types, the unwanted note types must have both fields present + an emptyFrequencyfield, which is considerably rarer than just having an emptyFrequencyfield.