clarify that both conditions hold

nexus/src/app/sagas/region_replacement_drive.rs

@@ -1368,9 +1368,11 @@ async fn srrd_drive_region_replacement_execute(
                     // If the Volume is active, that means reconcilation
                     // completed ok, and therefore Nexus can consider this
                     // repair complete. This is only true if one repair occurs
-                    // at a time per volume, and if this saga locks the region
-                    // replacement request record as part of it executing. If
-                    // either of those conditions are not held, then multiple
+                    // at a time per volume (which is true due to the presense
+                    // of volume_repair records), and if this saga locks the
+                    // region replacement request record as part of it executing
+                    // (which it does through the SET_SAGA_ID forward action).
+                    // If either of those conditions are not held, then multiple
                     // replacement calls and activation checks can interleave
                     // and confuse this saga.
                     //