So up until now, as long as you have spare attack robots you could just keep attacking with them. You got one free refresh of opponent and after that it was one doughnut per refresh, but the attacks themselves were OK while you had robots.
Just now I just did an attack that used some of my robots, but when I went to do the next attack even though I still have five attack robots available, it's telling me to pay one doughnut or wait ten minutes for the next free attack. This had to have just changed in the last day or so but I don't see any messages about it.
Given that we already had a cap on how many attacks we could do based on the number of robots, why the additional impediment?