So that makes sense, as the error is coming from the compiled routine code. 

But back to my original question: how do I enable the ^%ISCLOG that's described in the %occWorkMgr.int code?

I think it might be some internal syntax. When looking at processes, the %objlasterr value often has errors in that syntax: 

I edited out the namespace and classname for privacy. But the first and third marks are the namespace, the 2nd and 4th are the class.
Also, to make clear, no this isn't my code, it's in the error message being returned by the HS Compiled Routine. I imagine it's part of the internal workings. But I'm really trying to figure out how to get that ^%ISCLOG part to actually log.

They absolutely do and I agree that it's odd. I did a small typo, the parameters are "(.%p1, .%p2)". Obviously the namespace and class/method names are fake, but the syntax remains.