The challenge is that, even though those two phrases have very different tones, they quite literally are the same. Compensating for biased sampling is done by saying "well, I don't think this sample represents what I was looking for, so I'm going to pretend that some parts of the sample are less common than they really were and other parts are more common than they really were". The bias isn't an inherent property of the sample, it's an interaction between the characteristics of the sample and the characteristics we'd like it to have.