Se binds well with a number of heavy metals but does not help the body to get rid of them. Se just provides antioxidant protection while the HM remains in the body.
Since Se doesn't help the body to get rid of HMs, I bet this causes levels of Se in the body to rise. However I assume that the Se bound to an HM is not available for typical use--conversion of T4 to T3, etc.
I bet this would lead to hi-norm levels on a blood test but unknown levels of functionally useful Se.