If you are not familiar with the MkIII bolt heat treatment issues you must have never read any of the books on the Ross, nor examined any rifles that aren't new.
The Canadian Army effort to re-heat treat existing bolt heads while waiting for sufficient bolt head replacements from the factory are well documented.
In my collection I have 1 bolt which doesn't exhibit deformation on the left rear lug from impacting the bolt stop. Switching this bolt between several MkIII rifles turns each rifle in turn into a smooth joy to operate. Transferring the other rifle bolts similarly turns each other rifle into a jambing disaster.
Examination of the problem bolts shows very slight deformation.
I have 1 bolt which is badly deformed to the point of material loss, and have seen a dozen exhibiting similar damage.
I highly recommend obtaining "A Question of Confidence" from Service Publications. I have misplaced my copy, however it is based around a reprint of the 1920s investigation into the Ross and attempts to obtain the facts from the myths.
Bolt stop issues existed in both MkII and MkIII Ross rifles.
The split MkII** pattern of bolt stop was apparently an attempt to soften the impact of the bolt againt the stop, however these split bolt stops break...
Examine some Ross MkII bolts for damage to the bolt stop lug, then come back and tell us again about them not having problems. I have seen several which have had the bolt stop lug broken off of the bolts, deformation is quite common.