Why Asus wasted time in developing its own Clock app at all it's beyond me (*), when we can use more often updated and polished Google Clock app? I too missed above mentioned feature, so I must install Google Clock anyway despite that Asus Clock cannot be disabled.
(*) I am not dumb, I noticed that tabs are placed bottom on the screen, which is more useful on tall screens than top placed tabs and then there is even speaking clock feature (which I don't need as a Tasker user). But all of this is useless if you omit some basic features like the one discussed in this thread, or use a tiny thin and therefore hard to read font and waste 90% real estate of the screen.