I have never seen any official reference for this practice of grinding the bolt knob or receiver. Replacing the bolt body would be correct military practice. However, when you do not have an Ordnance system behind you, improvisation sometimes occurs.

A few days ago there was some discussion about bolt handle "flip" during dry and live firing.

Some of this can be attributed to striker spring torque. There seem to be several other factors.

Some of these are (may be):

Lee-Enfields have helical breech locking (1: 0.1" helix)
When the bolt is cocked, the striker is pulling the bolt lugs backwards against the helically cut shoulders.

When the striker is released, it is stopped suddenly when its collar strikes the rear of the bolt-head. This causes the entire bolt assembly to jump forward; moreso on an empty chamber. It will then rebound against this helix and thus be tempted to twist.

I have noticed that rifles with "bolt handle "flip"" tend to be generally a little "looser" than a new example.

When the action is fully closed, The bolt knob should not touch the side of the butt socket.

If the knob of the bolt handle is in contact with the butt socket, you can almost guarantee that it will flip to some degree when the striker is released. Bear in mind that the bolt body is not given a lot of lateral support by the receiver; bugger-all in fact. When the striker is released on an empty chamber, the bolt assembly will dance around in the receiver. The looser the fit, the more lively it gets.

Dig out your trusty early SMLE's etc and have a look at the bolthead and striker. The early pattern rifles had a striker with a lug that aligned with a notch in the bolthead to ensure the bolt was not misaligned (partially unlocked) at the moment of firing. The safety studs on the cocking piece and bolt body have a similar function.

Note also that Mauser 98's have an analogous system built into their striker and bolt body for exactly the same reason. The big slots on the bottom of the bolt body are not just to let gas out, but to allow milling cutters in to cut the slot that aligns with the "wedge" on the front of the striker collar.