If I go anywhere near one of 10 or so Indian Restaurants / Takeaways within my general roaming area, the aroma greats you long before you step over the threshold, and quite a distance away if your coming from downwind. The weight of the smell, and what it does to your appetite triggers, is undeniable, although I'm sure there are a number of people who hate it. Poor buggers really. Like people allergic to crustaceans, they need and deserve a telephone assistance number.
When cooking my base gravies, and dishes at home there is no doubt that I obtain a similar aroma, and it even lasted a day or so last week after a big days cooking, but it isn't anywhere near the pungency and character of the shops. Is it just the shear volume and variety prepared in one place? I'm not convinced of this, but it could be. I still feel that something is missing. I just don't know what it is.
I've never heard it referred to as the 5% but I guess it's as good a name for it as anything.