Note: This will only be testable at a higher friendship level, so as of the time of posting you can’t test it
My hypothesis is that the higher you get in friendship with someone the less IV’s will change and that Ultra/Best friends levels they’ll either stay the same or increase.
For example if i wanted to trade an 80% Magikarp with someone it should look like:
Good Friend: 50-80% IV reroll
Great Friend: 65-80% Reroll
Ultra Friend: Remains the same
Best Friend: 80-100% Increase
I’m yet to find a news source that discusses this so that’s why i’ve posted it.