I used to have constant header gasket leaks on my 408W Stroker until I found Earl's Gaskets with replaceable inserts.......never leaked again and never needed replacement inserts!!
I’d guess he’s talking about the crap you dump in your coolant as a bandaid.
With everything in proper condition there’s no reason a stock style head gasket on a mod motor should leak, shouldn’t need to do/add anything unless running crazy high boost