SAT Subject Math Level II

So, I am currently studying for the Math II test this upcoming October and this is my third time taking it. I took my first one May and my second one August and they both honestly were not up to par…
I decided to get a Barron’s book and Dr. Chung’s SAT Level II math. I decided to tackle Dr. Chung’s book first, and got a 720 on my first test. My second test I received a 650. This range was similar to my actual SAT Math score when I got it back.
However, I took nearly three months of IB HL Math and honestly learned so much SAT Math applicable skills and took a Barron’s test and got a 760.
So there was an obvious difference between Dr. Chung’s test scores and Barron’s test scores and this was most likely due to trigonometric functions that I forgot from PreCal. Dr. Chung’s test focused hard on trig identities on the practice tests which I do not recollect being present in the actual SAT test.
So, was this luck? or is there no need for me to memorize and go hard on trig rules, besides basic identities, rules, and functions.