Finding an approvalID on an issue: Why is this so hard?

Grok and I have been trying to crack this nut for an hour now. (I asked the AI Assistant and….let’s just say there were many 👎🏻s) Figured I’d ask the hive mind and--if I figure it out before anyone else does--I’ll post it here for everyone else.

The ask: I want to be able to determine the ID of an approval attached to an issue. The only pieces of data I have are the approvalProcessID (which I know because I have Fusion apply an approval process to these issues) and currentApprovalStepID. 

No matter what I do with that currentApprovalStepID, I just cannot get to the approval. If I try to use that to search for the APPROVAL object, I get a 400. If I try searching via the ARVSTP object, I get scolded that it’s “...not a top level object and can't be requested directly in internal”

There has to be something that both Grok and I are missing here. Any thoughts?