i) The meta-scientists concluded that much - or all - scientific research or testing involves at least some element of bias.
ii) This piece of meta-science is also a piece or scientific research and testing. Therefore it must have contained at least some element of bias.
Though does scientific bias also mean scientific invalidity? If it does, then this piece of meta-science is scientifically invalid: just as invalid as the tests on the button-pressing subjects.
“if the experiment is merely invalid (through careless procedure, lack of controls, etc.), its result may be true or false”. (130)
For example, the Pythagoreans believed that the earth was a rotating globe. Though they believed that for all the wrong reasons.
However, we're talking about scientific experiments here, not Pythagorean speculation or philosophy. In a scientific sense, if an invalid procedure or bias leads to truth, that would be of little interest to science or scientists. Indeed typical scientists (if they exist) would be hard-pressed to make sense of an invalid procedure or bias leading to scientific truth. Though perhaps either they too are biased or their stance on science is philosophically naïve.
i) We can assume that the meta-test is invalid.
ii) However, even though the meta-test can be seen as invalid, its result can still be seen as true.
iii) And, by inference, if the object-test can also be seen as invalid like the meta-test, then its results can also be seen as true (like the meta-test).