Starch plus amylase in the 140-160 F temperature range will give you fermentable sugars, regardless of whether it's boiled or not boiled. For the same reason, you can convert an otherwise poorly fermentable malt extract via a mini-mash with enzymatic base malt. I've done it. It works. If you wanted to run an oddball experiment, you could boil potatoes or rice into a sort of starch soup, then add malt and mash to convert it all to sugars. Yep, it works.