So it's an argument to point out the absurdity but it isn't ab absurdo?
Exactly, it isn't ab absurdo fallacy because there is no misrepresentation or exaggeration.
The concepts, while being obviously absurd,
cannot be disproved, which serves to illustrate the fact that claiming that something cannot be disproved is not a reason to take it seriously, let alone believe that it is true. Which is a point that some theists seem to find hard to grasp.
It is, in a sense, a
reductio ad absurdum (which is a valid argument, not a fallacy) of the argument: "you cannot disprove this, so you should take it seriously".
If someone were to claim that these notions were directly equivalent to theism in a wider sense, that may constitute an appeal to ridicule fallacy, unless they could point to another specific equivalence.