The passage tells us that the peers in question prefer the rigorous scientific method when possible. The passage later tells us around line 35 that the prevailing method of scientific rigor was to collect data with detachment from the subject. So, those peers would have had to believe that data collection did not necessitate deep immersion in the tradition in question.
I don't see any support for the idea that other social scientists think that dance experts are too preoccupied to conduct ethnology.