obviously you can use much to mean little with a how in front but generally with a little snarky aside like ", which is not much at all," after the "how much", but yes, in typical usage they are not interpreted the same, although I'd say the difference really only becomes important in comparative usage as in "how little for how much" and similar examples.
on edit: took out hows to avoid confusion.
"Surprised by how much" pretty directly means the amount is higher than expected. It has the opposite meaning the person intended. The neutral phrasing would be more like "surprised by the amount".