So in reply to Uplink...He is exactly correct...My experience with a major US carrier (Eastern Airlines) was shut down an engine on taxi in...But I was on the 727 and it was always #2...to lessen the footprint.
As far as powerback goes...yes we did that also...but only on certain gates at certain airports...Reason? Powerback requires a trained ground crew (with goggles) to direct you. Additionally, all GSE needs to be secured...lots of wind hitting the terminal, gate area...
Another issue was 2 engine powerbacks...we did it but only if taxi wgt was less than 160,000 lbs...(MGTOW of some of our 727's was 191,000)
It is always a physics vs cost over-ridden by safety
Sometimes good piloting, sometimes foolish...