Hello,
not really, the plugin does not do anything clever---it simply walks over the GHC core and renders whatever it deems necessary to JSON. The only extra bits it does is to make the unique names globally unique (I thought GHC already did that, but apparently not, perhaps that happens during tidying?).
I was thinking of trying to do something like this across compilations (i.e., where you keep a history of all the files to compare how your changes to the source affected the core), but it hadn't occurred to me to try to do it for each phase. Please file a ticket, or even better if you have the time please feel free to hack on it. I was just finding myself staring at a lot of core, and wanted something a little easier to read, but with all/most of the information still available.
It would be awesome to have a more clever tool that helps further with these sorts of low level optimizations---at present I find it to be a rather unpleasant task and so avoid it when I can :-)
-Iavor