Keep in mind the tach is showing a graphic representation of what the digital electronics are doing. Nissan likely sets the rev-limiter conservatively and may be adjusting for gearing and rate of RPM increase, like lower in lower gears.
Having a range of over-rev like to 8.5k is just old school tradition. Hopefully nobody ever sees this unless the ECU is tuned or they botch a 6 speed manual down shift. The Z's stock bucket followers and camshafts are optimized for max HP slightly below red line.
Most vehicles I've owned have the indicated redline a few hundred revs higher than the fuel cut.
Sometimes automatic transmission programming will shift even sooner than the fuel cut, can't have the automatic shifting too close to fuel cut.....