This feature doesn't exist. The Tesla home charger can share current with other Tesla chargers on the same branch. It can't share current with an electric water heater or some other non-Tesla load
There’s also smart breaker boxes that again have nothing to do with Tesla specifically. The breaker box will preferentially shed EV charging first when someone would otherwise trip their whole homes’s connection to the grid. It’s not a perfect solution, but sometimes your local utility doesn’t want to upgrade your connection to the grid because their substation is fully provisioned or whatnot.
They might be using one of these: https://www.chargedfuture.com/240v-outlet-smart-splitter/
There’s also smart breaker boxes that again have nothing to do with Tesla specifically. The breaker box will preferentially shed EV charging first when someone would otherwise trip their whole homes’s connection to the grid. It’s not a perfect solution, but sometimes your local utility doesn’t want to upgrade your connection to the grid because their substation is fully provisioned or whatnot.