No way to upgrade mints

I get that, but for each plant there are usually several upgrade options: paying real money, of course, but also by using gems, coins, watching an ad or even playing one of the levels where the plant is introduced. With the power mints, the only option to upgrade now is by paying real money. If that is indeed the case, then it defeats the whole purpose of the leaderboard of the Arena tournaments, since the top 8 or so places are rewarded with mints! What’s the point of trying to make it into the top three positions of the leaderboard if all you are going to get is a lot of extra mints that you can’t use for anything? Just to move up in the league table so you can then earn more useless mints? Right now it makes more sense to remain on a lower ranking on the table so you just win gems or coins which you can use actually use to upgrade plants.

Surely this is a bug on EA’s part, no? Or are they planning on getting rid of power mints and/or mints as an upgrade option altogether? I don’t get it.