There are some substeps of step 1 that cannot run in parallel. Therefore, for these substeps the amount of cores is less important than the speed. On the other side, for the processes that run in parallel, the amount of cores is very important and can reduce a lot processing time.
This Community post has some interesting information on the subject: https://community.pix4d.com/t/3787
Otherwise, to learn more about different processing performances, I could recommend this article as well: https://support.pix4d.com/hc/en-us/articles/115003928846
If there are other users who have some experience to share on the subject, feel free to add your comments! Would be interested to read about it.