Not really sure if this answers your question (I agree with you, ultimately), but here’s my experience:

At the college I attended, these sigma/pi expressions weren’t taught until the end of Calculus 2, but I wanted to take an Algorithms class - which had calc 2 as a prerequisite.

I got an exception from my advisor which allowed me to take Algorithms before the pre-req. In my experience, these concepts were easily learned in the context of algorithmic complexity.

Some might be barred from learning important theory in computer science by “brutal” math classes at university. They might find solace in this post which translates sigma into ‘for’