Does UC use ACT writing score?

[lkg4answers]

You must take the ACT with writing for the score to count.

https://admission.universityofcalifornia.edu/counselors/q-and-a/examination/

Is a student who takes the ACT required to take the writing section?
Yes. Students applying to UC who take the ACT must take the writing test to meet the UC examination requirement even though the ACT organization calls the writing section “optional.”