Thats some fair point. Though I think you are missing something. Player of a match is MVP, right? Have you ever seen MPVs of majors or other tournaments giving IGL? No you did not. That is because the IGL role is not under our sight and we cannot fairly estimate they impact - it depends on exact team, coach, second callers etc etc. Because of that the only criteria they use is HTLV game stats - 2.0, impact, assists, flashes, trades and all other.
And Nikos stats are a bit better than S1mples.
Anyway I think it is right to give it to S1mple. Because MVP goes to a looser only if there is no other comparable impact player on the winner side which is not the case.
TLDr; You are right, but not because Niko IGL