It's checking for features, not the version and browser. And as for features, UInt8ClampedArray is missing from IE (it was seemingly a late addition to Typed Arrays and might not have been picked up in time).

That being said, it appears that there is a slower alternative that works just as well, but someone would have to code up a workaround for IE in this case. I would have done it if I knew any JS (or CoffeeScript in this case).