Some entries don't seem as exhaustive as others I've seen. For example, there are only 2 entries for "a-": a-1 is for Greek "without" and a-2 is presumably supposed to combine all the various Old English senses though it only mentions one (Wiktionary, for example, mentions 5: "up", "on", "with", "of", and one without etymology).

But even if we allow that mixture, we're definitely still missing the Latin ones:

ex- turning into a- (blame the French) is admittedly rare so might be out of scope.

ad- turning into a- however is extremely common and definitely should not be merged with the Old English derivations (even though "on" often takes a similar meaning). This is noted on the ad- page but it needs to be mentioned under a- too.

ab- turning into a- is less common due to only happening before a few letters, but is not even mentioned on the ab- page.