It's a bit of a moving target as I'd understand it.
In the twilight of the Raj and the immediate end of empire (50s-60s), probably as you describe. In the 70s-80s, more an interpretation by Bengali restaurateurs of India's broad cuisine (with many invented dishes, and dishes given names from and inspired by Mughal courtly dishes from India and across India but loosely so in the facts of their preparation). In the 00s-10s increasingly something different again with clear aromatics beyond chilli heat and sometimes at the expense of chilli heat (initially the weakest link between "British" Indian and the real cuisine) becoming more prominent while recipes with rich and heavy gravies and starch are de-emphasized (initially the closest resemblance between "British" Indian and the real cuisine). And at no stage does any of the former ever go away, and its all adding to and elaborating all the time (plus some odd re-imports occur, like late 19th century British naval curries, in almost all the facts of their preparation and spicing, coming back via a Japanese detour).