Fix error in comment.

opm/simulators/linalg/StandardPreconditioners_mpi.hpp

@@ -276,8 +276,11 @@ struct StandardPreconditioners
                               op, prm, weightsCalculator, pressureIndex, comm);
                       });
 
-        // Only add CPRW preconditioners to the factory if the operator
-        // is an actual matrix or GostLastMatrixAdapter operator.
+        // Add CPRW only for the WellModelGhostLastMatrixAdapter, as the method requires that the
+        // operator has the addWellPressureEquations() method (and a few more) it can not be combined
+        // with a well-less operator such as GhostLastMatrixAdapter or OverlappingSchwarzOperator.
+        // For OPM Flow this corresponds to requiring --matrix-add-well-contributions=false
+        // (which is the default).
         if constexpr (std::is_same_v<O, WellModelGhostLastMatrixAdapter<M, V, V, true>>) {
             F::addCreator("cprw",
                           [](const O& op,

opm/simulators/linalg/StandardPreconditioners_serial.hpp

@@ -174,7 +174,10 @@ struct StandardPreconditioners<Operator, Dune::Amg::SequentialInformation, typen
 #endif
         }
 
-        // Add CPRW only for the well operator variant, i.e. --matrix-add-well-contributions=false
+        // Add CPRW only for the WellModelMatrixAdapter, as the method requires that the operator
+        // has the addWellPressureEquations() method (and a few more) it can not be combined with
+        // a well-less operator such as Dune::MatrixAdapter.  For OPM Flow this corresponds to
+        // requiring --matrix-add-well-contributions=false (which is the default).
         if constexpr (std::is_same_v<O, WellModelMatrixAdapter<M, V, V>>) {
             F::addCreator(
                 "cprw",