Nah, there’s nothing contradcitory about a hypothesis being both unfalsifiable and containing false claims.
For a simple example I might hypothesise that the reason humans have 8 legs is because God made us that way when he created us 600 years ago. There is no way to actually falsify the hypothesis while at the same time it is bullshit because the observation it seeks to explain doesn’t exist.
AAH is very much the same. It is unfalsifiable as presented and nonetheless bullshit because it seeks to explain things that don’t exist, like the fact that only humans can voluntarily control their breathing.
To extend upon that: one of the claims made by AAH proponents is that human beings cry and sweat a highly saline solution in order to eliminate excess salts that are taken on, presumably (the argument goes) as a result of injesting sea water. Now, we don’t fully know why humans–almost uniquely among mammals, sweats so profusely and cries whole tears. There are many hypotheses that seek to explain this phenomenon, and a valid one might be the need to eliminate excess salts ingested in some fashion; without further substantiation we can’t be certain. This does not, however, lead to the conclusion that we therefore must be derived from a species adapted to marine life; indeed, we’re incapable of tolerating even moderately brackish water for an extended period of time, and there is no vestigal indication in our physiology that indicates that we ever had this ability. (There is a further argument that elephants, being the decendents of a former marine mammal, also cry salty tears and this therefore “proves” that humans are adapted for life in the ocean, which neatly sidesteps the very contentious and unlikely claim that elephants are derived from some marine mammal.)
The fundamental premise of AAH–that humans adapted to stand and walk upright in order to wade in oceans, rivers, or lakes–isn’t falsifiable in the sense that one can argue that humans never did this or the need to do so doesn’t present some kind of evolutionary impetus, but it does not follow that therefore humans were adapted to habitual life in an aquatic environment, and indeed, nearly everything in our physiology indicates that we’re poorly adapted to functioning in and around the water. That we continue to do so–for transportation, fishing, et cetera–is a testament to our ability at behaviorial adaptation and ingenuity at figuring out how to live in and around environments that we’re not evolutionarialy adapted to survive in, like Arctic tundra, Arabian desert, or the unforgiving vacuum of space.
To claim that a few independent features–adapted for whatever reason–“prove” a hypothesis so unsupported by fossil evidence, vestigal anatomy, and evolutionary zoology is what Francis Bacon called “counting the hits, and forgetting the misses”, i.e. the fallacy of selective observation. Some of the claims may be unfalsifiable, but the lack of cohesiveness or external support for the argument also make it unlikely to the point of nonsense.
If by unfalsifiable you mean “some part of the hypothesis inherently cannot be proven false”, then I agree. I guess I would say “partially unfalsifiable” instead.
Why isn’t “humans adapted to stand and walk upright in order to wade in oceans, rivers, or lakes” falsifiable? That seems like something the fossil record could potentially disprove (and perhaps already does). Are you saying that no fossil could in principle disprove that statement?
How would you verifiably disprove this claim? You could provide a more likely explanation–say, that humans evolved upright statue in order to have better visibilityin grassy savannahs–but you can’t rule out that the ability to wade had some impetus upon the development of upright stature and plantigrade articulation. Certainly, fossil remains are found in and around rivers and lakes, indicating that hominids sometimes lived near water. But by itself, or even in collection with other isolated factoids, doesn’t support any serious arguments toward the AAH.