First gear is usually shifting at a lower RPM than redline anyway. I'm not by my tuner to see what WOT shift point is set at in 1st, but I know it's not near redline.

Another point is your computer can be set to shift at 5700rpms, but not actually shift until 6000rpms depending on the tranny.

Another point is if you actually look at the gauge in your car and then at the scanner to see what the pcm is seeing for rpms the dash guage is off.