First, I think he didn't made that point very clearly. Second, why would they be sold at a larger discount than larger holdings? It is all in proportion - they own less and sell less of the smaller holdings.

(There are issues conceivable where you have a liquidity mismatch (bonds, real estate), but I haven't seen a solid elaboration of that point. It's the good old "people worry about bond market liquidity" meme that Mark Levine pokes fun at in his Bloomberg Column "Money Stuff".)