Sharing sortings

Maybe I didn’t understand correctly the property USE SEPARATE FOUNDSET:
shouldn’t this property also extend to Sortings?

I have a tabpanel showing records from lineitems1
I have a method (Show_Details) that shows all the lineitems of an offer on a different form (lineitems2), set to use a different foundset, sorting per orderdate.

Why, when I switch back to my original form, I see the items in the tabpanel lineitems1 sorted like they were in lineitems2, instead of leaving them as entered?

Is it an expected behaviour?

Did you set the form showing in the tabpanel to useSeparateFoundSet? can you reproduce this in a sample?