When you make a selection on an expression, you are actually making selections on the underlying fields. Depending on the expression, this may give results different to what you expected. If you display a current selections box you can see exactly what selections were actually created.
The reason is that the expression value is a transient value meaningful only in the table. Selections are done on fields which persist throughout the model.
If you replace the expression with a derived field calculating the expression in the load script, you will be able to make simple selections on the derived field.
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein
