Back when I was still a shitlib, The way I looked at it was that intersectionality was a method of scoring/ranking individuals for privilege/oppression based on a number of attributes (eg. race, sex, sexual orientation, etc...).

Then identity politics was the value judgement of, once you have this raking, how to you allocate resources and extract taxes on the basis of this ranking?

I do not know if that was an accepted way of distinguishing between the two or if that was just my own personal way of "polishing the turd" to make sense of nonsensical ideas.