Remove refer a friend growth boost

Referring a friend is great for the game, one new player, and the cosmetic rewards are only obtainable via this system. This is perfectly fine, I can live with it, there has been exclusive skins before. The issue I have is the GROWTH BOOST.
Yes its only with friends you referred, but giving people an in-game advantage because they paid extra money or got someone else to is plain and simple unfair. Not everyone can afford to buy their friends games, not all peoples friends can afford the game, hell not everyone even have friends that like PoT. This is especially annoying to solo players like myself, being at a disadvantage because my friends don't want to pay 30 dollars for a game they have no interest in playing.

TL;DR, getting other people to buy the game should not give an actual gameplay advantage. Cosmetic rewards are fine, actual in-game boosts to stats (growth speed in this case) are not okay.