Very interesting thread this.
I believe you come to your own conclusions after experimenting for years taking in consideration all your curry experiences over that time,I have cooked a curry in two separate takeaways plus had a days tuition in a Indian restaurant kitchen that specialise in 'traditional' style curry's that are made using very finely chopped onions and tomatoes to create the curry sauce/gravy and very nice too

In my opinion 'the taste' needs to be in the gravy from the start and spices etc added at final cooking are only added to differentiate one dish from another.
My local where I cooked a madras use the 'all in the base' method where their gravy is basically a finished curry with only the odd ingredients are added to produce the desired dish and their curry's are very good.
When I think about it 'that taste' is the curry sauce in my curry the meat or whatever tastes of whatever the product is plus a light spicing probably from a marinating process but the flavour I really like is in the sauce.
I have made countless base gravy's and the finished flavour in the recipe is 'a mild onion soup' type flavour
Then on making the curry's even after adding spice at the final curry stage ends up dissapointing once again

The best results I've had from memory was from the admin base which uses quite a lot of garlic and the gravy has that 'finished curry flavour' .