I agree with the 90 deg on NAT Tracks.
Some years ago I was taught to turn 60 deg off whilst conducting an emergency descent and our SOPs still refer to using the heading bug. But, I have never been able to find reference to this heading change in any manual. Seems to me a hangup from when we were flying along airways and turning 60 deg would get you quickly displaced from the centreline. Seems a bit irrelevant these days when direct ..... seems the more usual routing and the chances of someone being below you are minimal (unless someone can let me know otherwise). However, can see some merit in reducing negative G (or less positive G!), but also support the lots of things to do anyway and adding a requirment to disconnect the AP to get 45 deg AOB seems a little like leading to getting overloaded.