My two cats each have their own toilet so I can train them each at their own pace. My quick learner, Solo, is on the intermediate green stage, the slow learner, Kronos, is on the beginner amber stage (with the tiny hole). Both are using their toilets for pee and poop very well thus far, although after much difficulty with the slow learner!
I was so proud the other day when Kronos, on the amber beginner stage, went to pee in Solo's toilet that had the green intermediate ring! I was so surprised
It just goes to show that peeing is no big deal, but for some reason our kitties are much more finicky about where they poop.