I don't know why you'd want to point your domain to an app that's only up half the time anyways, so I don't think this is a big deal.
Domain redirects are useful for portfolio apps if you'd like to have some coherency in your urls, and maybe you're not trying to showcase that your app is on Heroku's free tier at that moment. That's legitimate, it's also a use case where 12 hours/day is likely sufficient. However users breaking TOS and keeping those apps awake 24/7 so recruiters don't have to wait ~30s for them to load is probably a problem Heroku's trying to solve.