Why not show actual percentages instead of Tremendously, Moderately, etc.?
This would take so much confusion away especially for newer players. I have a friend that is just getting into the game and he is constantly bringing add-ons for survivor and killer that are practically worthless, but because of the wording of the descriptions, he thinks that they're amazing. Things like Demo's red moss that says TREMENDOUSLY increases the undetectable status after exiting a portal but it takes it from 2 seconds to like 2.5? That's just purposely misleading and confusing especially to new players.
I honestly don't see what the downside would be, it's much easier to understand numbers and percentages than it is for words like moderately, slightly, etc., especially if you don't know the base value of that add-on.