It is interesting that they removed they didn't allow positions that resulted from captures in the training dataset. I wonder why would that affect negatively t

It is interesting that they removed they didn't allow positions that resulted from captures in the training dataset. I wonder why would that affect negatively the results. The explanation they give (opponent will likely capture back soon) does not sound enough to me. The tactics of the position should capture that. Is this because it is hard for the network to learn from positions with less material and tactical opportunities?