No, not correct.
GMail + BIS supports wireless delete reconciliation. If you delete from GMail, the deletion will reconcile to the handheld using BIS. (It does take a while... sometimes hours, so be patient.)
The same is true for deletions from the handheld. They will reconcile to GMail as well.
Read/Unread marks will only delete one-way. (Handheld to GMail)
You can read about the BIS features here: View Document