Ignorance?

Question

I realize that there is a lot of ignorance out there with regard to Pesah laws, but how do you explain the fact that knowledgable rabbis are also spreading some of this misinformatioin? For example, in Rabbi Shimon Eider's book on Pesah he mentions that some poskim forbid paper plates because the starch in them may be from hametz (this despite the fact that a paper plate is inedible). These poskim are clearly not ignorant, so where are they getting this stuff?