Idk anything about the specific tires you're referencing but I know that most tests have found a 1-2db difference in OEM tires with and without the foam inserts. 9-10db is a massive difference since the noise is measured logarithmically - this does not sound correct at all.
I may have misheard him, but I thought he said 9-10 db with the foam inserts. Sounds like you know way more about the way this works than I do. Sorry for any confusion.