It's just because Islamey has that reputation. It is not that hard.
Having said that, it is not easy. I suggest that until one has played the piece in concert, they should refrain from calling Islamey, or any other piece, easy.
I've played Islamey live in concert, and some of you may have seen the video, but I am nothing yet like Pletnev. If anyone's interested in the video, you can still find it here:
https://cafemaru.net/e60m5/islameyhi.wmvor
https://e60m5.ath.cx/islameyhi.wmvIt takes time to download, though.
AND I AM AWARE that it is not the best of performances. Yet, nowhere did I claim to be the best of pianists. ;p The video was from March 2003, when I was 15 years old.
My personal thoughts on the piece are that if you have the correct technique, Islamey falls from being fiendishly difficult to being manageable. But no matter the technique, it will never be a walk in the park.