It makes sense to do the base like this.
In Indian cooking, especially the northern styles which so much BIR is rooted in, it's quite common to cook ingredients more-or-less in their own moisture - only adding water later to acheive the correct consistency to the gravy.
It'd make more sense commercially to do it like this too as it's easier to add moisture than to take it away, especially with the massive quantities as shown in this video.
gary