That's another wonky workaround.
Parents CAN'T limit apps in their entirety, you must set a 1-minute limit. So, the moment any of my kids access an Apple device, they get a slew of messages their app limits will expire in 1 minute. Even I have to admit to them, "Yeah, it's dumb."
And then there's the 11:59 PM setting if you want to block out an entire day, for example, if you want to limit apps to weekend use only, all the weekdays have to be set start at 11:59 PM (and end at midnight); I suppose that's a feature not a bug.