If you’re talking about the handle overlay, the difference is that CV-MAP is using the Rack API’s functions for establishing lazy handles for parameters.
I did (in V1, with sadly no estimate for when I’ll be able to bring it over to V2) a fair bit of work on module overlays and my suggestion from that experience is that you manipulate other modules only through the Rack API; if you want to update something visually, build an overlay and drop it in the correct location.