Black water disposal for permanently parked RV

someone did suggest getting the septic tank drained more often if the black water or grey water are drained into it,

Maybe just a matter of semantics, but when you have your tank pumped out it is not to "drain" it but to pump out the solids that have accumulated on the bottom. The leach field is what drains your tank and is what you need to be concerned about. If only the black tank is to be emptied I would not be concerned but the rest of the water use would be of concern.