Contradicting midrashim on Circumcision in Egypt

Dear Rabbi, It says in Rshi (Meketz 41/55), "for Yosef would say to them that they should be circumcised". Pharaoh agrees-so all men are circumcised". In Vayigash 55/4, Yosef (according to Beresh’s Raba, which Rashi brings) shows the brothers his circumcision as a proof of him being a son of Yaakov. How is this a proof if all Egyptians are circumcised?

Shalom! The general rule that one cannot ask questions on midrashim (Rambam, Guide For the Perplexed, p. 15) is based on the fact that some, probably most, midrashim are not factual traditions but rather educational vehicles for teaching us philosophical or spiritual idea/s, or how to act properly (sometimes writing anachronistically about our forefathers, where the real intention is to teach a needed lesson to the listeners of future generations), while only some apparently come to fill-in ancient traditions. Others may come to answer textual questions. In other words, one or maybe even both of these midrashim aren’t meant to be taken literally, and accordingly there is no significance in asking about such apparent “contradictions”, but rather to learn each midrash separately, for what it’s trying to convey. Shabbat Shalom! Rav Ari Shvat