A recent model ZR1 would be going 130+ in 6th gear at 4000 rpm. So, you have to take it fairly easy during break in (it would have to be a quite leisurely acceleration to 130, granted), not as fun as after break in, but it’s not 30 mph. 
(owner based, but no reason to doubt this graph in general AFAIK)
'Zactly–to all intents and purposes there isn’t a breakin period, they’re just cautioning you not to take it straight from the factory to a race track, which seems like just common sense to me. Normal street and highway driving isn’t going to stress out a 'Vette in any real way, and acting the fool in your brand new sports car is a stellar way to end up with a very expensive ball of metal. Me, I’m old–I like to drive pretty fast but not ridiculously so and a cross country road trip in a brand new 'Vette is something that scores pretty high on my bucket list meter.
Besides, even if I were to want to redline it right off the bat, well, 500 miles from Bowling Green is around Kansas City so I’d stop into a dealership there, let them check it over and do anything that needed done and then I’d be on my way–about 2300 miles plus that I could drive with throttle wide open if I were silly enough to essay the experiment. So yeah, in my case the factory to home road trip would be fuckin’ fantastic.
I work for a Chevrolet dealer and the 500 mile service for Corvettes is considered the break-in period and your first oil change is done at that interval as well. The 'Vette is the only car that GM makes that has this that I am aware of.
You’re all ignoring the other salient point: “Avoid driving at any one constant speed, fast or slow, including the use of cruise control.”
Cross-country trip, constant 75 to 80 mph… I suppose one could use surface streets the whole way, but there are large swathes of land where “surface streets” are cross-country at 55 mpg posted.
Now that’s some Jimmy Carter-esque regulation. “Fast as you want, as long as you’re getting 55 mpg.” 
Like I said before, my current car (M2) also had fairly tightly specified break in period and 1200 mile break in oil change service. So as I mentioned, taking delivery in Germany, then head to no speed limit segments of Autobahn!..oh, but you’ve have to limit yourself or else run up 1200 moderate miles and get the break in oil change while still there. Similarly if taking delivery in SC they’d do a nice program for me but I couldn’t go even reasonably legally ‘all out’ on the 700 miles home. But as it was, I took delivery locally (NJ) and ran up most of the 1200 on country roads in PA (I don’t drive to work nor use that car locally otherwise all that much). That was pretty fun. To me ‘road trip’ is definitely not constant 75-80 mph implying to me Interstates. We took the car on 5,000 road trip this year, maybe 10% Interstates. Mainly country, mountain and coastal roads where frequent speed change is more natural. So even during break in that was pretty fun, just couldn’t floor it/kick down to pass on two lane roads or, to a lesser degree, ‘dig out’ of corners with a lot of throttle. But once past the 100-200 mile interval where you should also go easy on brakes and tires, I could still brake hard/late into curves and pull some lateral ‘g’: fun. Although being able to fully use throttle (even though an M2 not as much of a raw power car as upper end Corvettes) is more fun. As to really high speed I got the car up to the electronic limit (155) on a road with nobody, for miles of desert, but otherwise I only reach low triple digits occasionally flooring it on two lane road passes to get past as quick as possible. I go 60 or so on 55 ‘country roads’ (though some of those are posted up to 70 when get out West) and it’s plenty fun IMO to have a higher performing than avg car.