I haven't tried this yet but I intend on doing so. RJ is one of my favourite dishes but unfortunately some recipes are just awful.  A good RJ is a lovely thing though, and knowing Razor's reputation, I'll be looking forward to this one.  I'll do lamb though.

Here is the recipe written out, as taken from the video.  Very nice too.

Staff Chicken Curry

Ingredients

1kg Chicken pieces on the bone (wings)
4 Chefs sp Veg oil or veg ghee (8 Tbsp or approx. 1/2 cup)
2 Indian Bay leaves
1/2 stick of cinnamon bark
7 whole green cardamom pods
5 cloves
3 medium onions chopped
1 green chilli chopped
2 Tbsp Garlic Ginger paste
Fresh Coriander chopped
3 Tbsp Mixed Powder
Chilli Powder to taste 1/2 - 1 1/2 tsp
1 tomato cut into 8 pieces
Hot Water as required.
Salt to taste

Method
Heat oil slightly and fry whole spices
Add onion fry for 1 minute
Add green chilli fry but do not brown
Add G G paste and continue to fry till translucent
Use water if necessary to avoid browning
Continue till onions melt.
Add 1/2 handfull chopped coriander
add 3 tbsp mixed powder and chilli powder to taste
Fry lightly then add some water if necessary
Cook for 2 minutes
Add chicken pieces and stir to coat
On low heat and with lid on cook and stir at 5 minute intervals 4 times.
Add tomato and cook for 5 minutes lid off
Stir and add more coriander (not too much)
cook 5 more minutes
Done.

Unfortunately my wife was mainly wait staff, not kitchen although she did help out. However, she did learn a lot there and on top of that she was an exchange student to Sri Lanka for 12 months living with a host family in Colombo. The family network connections was how she got the job back here.  We enjoy many different styles of food, which I prepare mostly as she is simply too busy.

Just like in a BIR, the Sri Lankans used pre-cooked meats and gravies so the time to actually cook the final dishes was not the main consideration.  The day before preparation wasn't simply for speed. Flavour development was a big factor in doing this.  The restaurant in question was run by a Sri Lankan family but they did serve standard Indian dishes as well.

I have always found that red meat dishes like stews, casseroles and curries always develop a more rounded and full flavour after a rest period.  This is also noticed by people who didn't cook it so the lazy palate idea is not necessarily a factor although it may well contribute and probably does.

There are 3 distinct possibilities, and probably others contributing factors.
Number 1 is the base is too heavily flavoured as you have mentioned, and so this flavour carries over into every dish.  If you are using one of the many bases here though that would be unlikely, but you could try watering your base down as is often recommended as the final step.  A step which many choose to ignore by the way to save freezer space.

Number 2 is that there is insufficient variation in the spicing and additional ingredients in the finished dish.
There was a thread here not too long ago, in which someone gave a very simplified method of cooking where all dishes were prepared exactly the same and only very slight variation of chili levels and other spicing was used to create all the differently titled dishes. I can't see that approach myself but who knows? I never tried it.  I may be wrong but it could have been Korma Chameleon, about a year or so ago.

Number 3 is the strength of flavours in the pre-cooked meats if you use them.  I've been doing Kushi pre-cooks and they do have a very strong influence on the finished dish, particularly if you transfer some of the pre-cooking liquid over as well.

When I am cooking a banquet style meal (usually) I always try to make dishes that are deliberately quite different to avoid this, so for example I'll do a lamb Rogan Josh for spicy / hot, either a lamb or chicken Madras for tangy, a creamy Mango Chicken for sweet, a nutty Korma, a tomato based Vegetable curry like a Navratan with Paneer, a pulse dish like Rajma Masala and / or a Dal. I've recently been adding the traditional Staff Curry and found it adds a good variety and is delicious, as does a lamb mince Keema.  I rarely cook Vindaloo but I have some diced pork in the freezer so it will be on the list soon.  The CTM added lately was very good and different.

You really have to force the variety into the BIR cooking method.

When I have a curry cooking day I usually spend all day at it and do 6 to 8 dishes and try to vary them as much as possible.