This is a limitation to the Multiple Item Add to Cart interface tutorial. that tutorial is geared twords adding multiple simple items to the cart. That is to say items that do not have options like color or size.
the Problem is this:
The Item ID is passed to the DataAssist Search server behavior to filter the recordset.
Once the recordset is filtered, the Add to cart from recordset behavior loops throughthe recordset to add each itme to the cart.
While looping through the recordset, it is impossible to also loop through the forms collection to match the appropriate Color or Size Select list with the item that is being added to the cart.
It is the same limitation that is causing the quantity not to work.