Axe,
I've also considered this theory too. I wonder at what point in time did they (BIR's) start to tone down their dishes? I certainly can't put my finger on it!
The trouble with this whole 'old/new' thing is, the permutations are endless

The regional variances,
The origin of the chef,
The amount of ale consumed :

The good and the not so good restaurants
The time of service,
Each of which can apply to the old or new style. It's going to be difficult for us to replicate any dish, from any era and get the whole forum to agree, that we have cracked it.
With that said, I am getting some really good results using my base, spice and onion paste, very much lending itself to what I remember as 'old' style BIR. I made a Madras last night which was excellent. I didn't add any extra salt, and I'd run out of tomato puree, so I used.......wait for it........tommy ketchup instead

This along side my onion paste add a lovely sweetness to the sauce, without adding any sugar, which I was well chuffed with ;D
I'm actually thinking of replacing the tom puree with the ketchup as standard but, I will need to prove it out a few times before I settle on this.
Ray
