Well R6 claims peak HP at 14.5K, after which the over revs will flaten and maintain the peak power, which I'm guessing in reality the peak power HP would drop some but still allow the rider to maintain the pace out of the corner. It's not practical for long straights, but it does eliminate the need for upshift through those short straights before another corner. This is still ingenuity on Yamaha's part, considering on all other 600's over revs end at 1000 rpm earlier, while Yamaha is still pumping power.
It's that sort of thing which made first-gen R6 fast when it came out. Considering my bike ('99 CBR600) made more HP than '99 R6. But with 12.5 peak power and 13.5 redline, F4 ran out of steam. Both making high 90s HP at the rear wheel (F4 making a couple more ponies), while R6 putting its peak hp at similar rpm range, still carried about 85 hp well into 15K redline.