Myself, I flatbase the cat tracks by twisting the board torsionally alternating toe and heelside with emphasis on the front foot. Like initiating a turn. Once you get a hang of it it's not a problem. I think it makes sense to not have a very stiff board, but I checked up that board you rode and they say it's soft and playful. So it's likely just your technique.I was also struggling with this on my japan 2018 snow trip (first time snowboarder). I was on a rossignol district 2015 board as my learner board (20% camber in the middle and 80% rocker everywhere else). This was fine in furano where it was all big wide runs, but when we moved to tomamu there were a lot more cat tracks and I struggled big time on them.
I am planning my next trip now, is there a board profile that is more optimised for going straight down cat tracks? Any boards I should look at as my next board with this in mind? I plan on starting next trip with some lessons focused on this as well, but my wife and son loved these paths, especially the ones that went through the trees so I would like to do these more on the next trip.
I totally get having a board that is good for riding in places that your family likes to ride, but I bet you don't just ride cat tracks. Focus on a board that you can have fun turning at their speed instead. My family also likes cat tracks or narrower, winding and faster green/blue runs, but we also ride wider more open pistes as well.
Could try something with lifted edges near the contact points. Like the Bataleon or maybe the Jones. Or just practice more