I was asked roughly this question by someone I don't think was interested in an answer so much as trying to get ammunition for his claim of "conspiracy theory." He shall be nameless here. The fact is that I am not sure. I do know this. Scientists had reached a point (and rightly so) where "godidit" was unsatisfying as an explanation. But they are human and humans don't like to say "I don't know." So was opportunity for such a bias, particularly since no acceptable alternatives existed. Even I refuse to accept "godidit" as an answer. If I am amazed at the intricate design work on a building, I am interested in knowing how it was accomplished. A source of "Acme Construction" does not answer my questions.
Closer to the heart of the idea, I don't see that we can conduct an actual test. The only "thought experiments" I can come up with involve taking direct observations over millions or billions of years. The direct observations would be necessary so that a missing animal would really be negative data. The only approximation we have are fossil digs and missings fossils are excused by the rarity of fossilization.
I have seen much of the positive data and the idea is certainly plausible. But I am a stickler. A scientific theory must be subject to falsification attempts. In any of the "tests," absence of positive data, would not be considered negative data. Consider, the recent discovery of the centromere/telomere patterning on human chromosome 2 is supportive and serves as a plausible explanation why we have one fewer chromosome pair than other primates. But, suppose there were no such find on any chromosome pair; would that be negative data? Of course not. If it would, then the many variations in chromosome counts of animals would also be negative data, and, indeed, catastrophic to the hypothesis. If there were no such find, an easy explanation would be that mutations had washed out the patterns. Alternatively, one might suggest that any relevant genes had been transferred to other chromosomes and that the resulting unneeded pair had, through successive generations, not been transmitted.