I believe the point (and this is what I would say too) is this offline and responsive apps already exist, thanks to the excellent API.
I’d rather the Tofugu team put work into the site itself, rather than replicating work already done by 3rd parties to make apps. I’m sure they could make a great app, they’ve certainly the tech and design skills, but do they need to? If I was them, I’d probably have a kanban/trello board with stuff ordered by how much the average wanikani users experience would be improved and a mobile app would be way down on that list.