In an ideal world, yes. In an ideal world, your hay would be laid out in one loooooooong windrow, with absolute uniformity, where you'd never need to turn around, speed up or slow down, the hay isn't blown around, there is never a problem with the knotter, twine, tractor,  trash or critters in the hay, etc. You'd get the tractor going at exactly the speed you need to make "X" flakes per bale, you'd tie the steering wheel off to a door handle and you could kick back and go to sleep.

In my admittedly limited experience, the world of making hay is never ideal and from my admittedly limited experience, the reliability of the baler is much more important than the theoretical capacity. A wicked-fast baler that you have to constantly tweek and tune up when you need to be baling hay is worse than useless. The times you will be able to observe anything close to the theoretical capacity/throughput of a baler you will be able to count on one hand per season. Shoot for 15 to 18 flakes per bale, but be concerned more with how uniform the "feel" of the bales coming out is -- you want bales that will stack well and the customer likes. Big flakes make for unstable bales.

In those rare cases you are able to achieve near-theoretical throughput, do not notice it. Don't get happy or pleased with the results. Every time I've done this, The Almighty has seen fit to immediately punish me for hubris. Maintain a dour and grumpy demeanor, no matter how many bales a minute you're getting out the back end of that thing. 

That said, I run our hay operation on Hesston balers, albeit the three-string 4690 "big brother" of the 4590. Hesston balers are more reliable than any other baler I've seen put next to them. Depending on the type of hay, we shoot for 18 to 25 flakes per 43" long bale, from 100 to 140 lbs. Your bales will be about 1/2 of this weight, depending on what/how you're baling.