Energy ICs don’t have to sit directly on one of the supply rails - in this case I think that’s more a function of them using a shunt. If you stick with CTs for measuring I (especially 333mV CTs that effectively come pre-calibrated from the factory) and a precision divider for V, you can get some pretty spectacular accuracy even without mSure. There are techniques for ensuring there’s plenty of R between the IC and either of the supply rails.
I should have added, in case anyone is thinking of replicating that, that’s in addition to isolation, not instead of isolation.