They way I heard, I really have no idea if this is correct-- The SHA256 function is on the chip because scrypt coins still use some SHA256 in their workflow-- thus the SHA256 hardware is necessary. The dual mining is a bonus from that requirement.
yep, the way I read script mining was that it was X iterations of SHA256 for each script operation where X is what the script part deals with along with using the results per SHA256 in to the next SHA256 of the single Scrypt hash. whole lotta SHA256 hashing per 1 round of scrypt hash. If I found out what X was, i'd prolly already have worked out IF i can move my Erupters to a dedicated PI based scrypt miner