Is the source related to rav kook, heter for shemen kitniyot or is it similar to the heter for soy and quinoa which did not exist at the time of the gezera?
I'm not sure this was downvoted at the time I answer this. I was discussing this question with my rav earlier this evening.
We both recall in the 60's and 70's that one of the "staples" of Pesach grocery items was Planter's peanut oil with an OU certification. It seems that at that time, OU did not rule against kitniyot extracts even though they forbade peanuts themselves as being kitniyot. (I don't recall if based on that reasoning, if OU allowed Wesson corn oil. They might have.)
As you know, kashrut certification is largely driven by politics as well as "demographics". I.e., if a large percentage of the population is for or against something that drives the marketing of product sales, and, in a sense, kashrut certification. So, at some point, probably in late 70's - 80's kitniyot extracts were considered forbidden on Pesach and the prohibition against certain "seeds" were added to the prohibition of kitniyot as well. (I recall eating sesame honey candies on Pesach with a reliable hechsher (don't recall if it was OU or circle K or what.) Now, no sesame (or poppy) seeds allowed.