Additional Rogue Exile Idol mod

The mod "Your Maps have a #% chance to contain # additional Rogue Exiles"
currently scales multiplicatively.

If you have two "Your Maps have a 10% chance to contain 10 additional Rogue Exiles" mods on your idols you will get 20% chance for 20 additional Rogue Exiles instead of 20% chance for 10 or 10% chance for 20.

Is this behaviour intended? Will I get banned for using it?

Any updates on this from GGG?
This is necropolis all over again with the silence and prices shooting up. This one mod is over 8 div each. I want to invest but dont want to waste all my currency on it for a nerf to hit.