Hi Phil,
Here in Australia it is very different, I've been in two restaurants, still in one of them and had a couple of chefs out to my place for some lessons.
None of them use gravies the consistency I see in the vids/recipes on the site. And none of them use just one gravy to make all their dishes either. This could be due to these being restaurants where you dine in and have a small takeaway market compared to pure takeaways perhaps in the UK. Our curry market here is nothing like the UK.
All of them use very thick pastes which water is then added to at the dish making stage. This provides a concentrate gravy/gravies which take less room in the fridge, and for us at home in the freezer.
Stock is not added per se, however the pre-cooked meat(chicken/lamb/beef) when added does have some of the cooking liquid with it, so there is some additional flavor that comes through from that being added.
And being a smaller quantity when defrosting and having less water amount in it, does unfreeze a lot quicker.
Regards,
Mark