jb, it's clearly a regional thing but you've mentioned Dave Loyden's book which was from an actual BIR and so that is direct evidence that it is used. I'm not claiming that it is used widely, just that it is used.
I happen to love the stuff and am quite atuned to its flavour so can detect it in some of the BIR curries I've had, in particular Vindaloo.
But this is to get away from the point I was trying to make, which is that any competent craftsman knows the tools of his trade even if he only uses a subset of them and I have little faith in anyone who does not show this wider knowledge.
I just wish this establishment was closer to me. I could then visit and hopefully be pleasantly surprised.