Alternative point of view, separated for clarity:

"seeking out all things that are not black and checking they are not ravens."

This statement seems a faintly ridiculous idea. Our mental model holds an infinite number things that are "not black", so there are still an infinity to check. Checking one thing should not change our internalised probability at all.

Even if you disagree that there are an infinite number of things, checking all apples contributes 0% towards this case - and is surely no easier than checking every raven.