I've found the adobe reference to be lacking in this regard as I've been unable to refer to the gray working color space accordingly.
The reference says that using a string with "Working Gray" or "Working RGB" should refer to their respective working color spaces. In my experience I have not found this methodology to work.
I can successfully change profiles by doing something like this:
docRef.convertProfile('KMattePr_50_3_14-3-12.icc', Intent.RELATIVECOLORIMETRIC, true, false)
but I cannot get it to work this way:
docRef.convertProfile('Working Gray', Intent.RELATIVECOLORIMETRIC, true, false)
Given that I'm trying to refer to the "Gray Gamma 1.8" icc profile, it seems like I do not have another option to access it aside from making it my working space and referring to it accordingly.
Indeed I did, thanks for the tip.