I guess this is likely a net positive for me being based in Denver, but I'm sure there's some example of reasonable connections that leave right after midnight that probably should have been exempted from this rule.

I still see some examples with overnight connections in Vegas that show the old price ($31) but if you click through it tacks on the early booking fee. Which is of course illegal now, but Frontier's sad IT can't be expected to follow laws.

Edit - thinking more, this is a huge problem for international bookings. You have a 10 day window to book intl itineraries but now you can only book the intl segment ahead of time then hope for the best for the domestic segment or pony up cash...?! Then also assume all the risks associated with having separate tickets instead of a single multi-leg itinerary?! Asinine.