[COM API] Mixed result with creating Vault structure through code

Working on something fun, but having mixed results: can't get a perfect result with creating structure through code, using AddObjectTypeAdmin, AddPropertyDefAdmin, AddObjectClassAdmin.

Expected: creating an OT "Log", PD "LogMessage", a CL "Log" through code and aliases for each.
Result: an OT Log, PD LogMessage, but TWO "Log" classes (with sequential ids), where the first has become a "builtin" class (when I try to delete it from my local vault)!
See screenshot

It's a bit of a hit or miss with examples lacking for AddObjectTypeAdmin, AddPropertyDefAdmin, AddObjectClassAdmin

This is my code. What am I missing that causes two Log classes to be created?

var logObjectTypeID = vault.ObjectTypeOperations.GetObjectTypeIDByAlias("OT.Log");
var logClassID = vault.ClassOperations.GetObjectClassIDByAlias("CL.Log");
var logMessagePropDefID = vault.PropertyDefOperations.GetPropertyDefIDByAlias("PD.LogMessage");


 // Add Log ObjectType if it doesn't exist
 if (logObjectTypeID == -1)
 {
   ObjType objType = new ObjType()
   {
     NameSingular = "Log",
     NamePlural = "Logs",
     AllowAdding = false,
     AllowedAsGroupingLevel = false,
     RealObjectType = true,
     CanHaveFiles = false,
     External = false,
     ShowCreationCommandInTaskPane = false,
     Hierarchical = false,
     HasOwnerType = false,
     OwnerType = 0,
     Translatable = false
   };

  var objTypeAdmin = new ObjTypeAdmin()
  {
    ObjectType = objType,
    SemanticAliases = new SemanticAliases() { Value = "OT.Log" }
  };

   var newObjTypeAdmin = vault.ObjectTypeOperations.AddObjectTypeAdmin(objTypeAdmin);
   logObjectTypeID = newObjTypeAdmin.ObjectType.ID;
}

// Add LogMessage propertyDef if it doesn't exist
if (logMessagePropDefID == -1)
{
   var propDef = new PropertyDef
   {
     Name = structureConfig.LogMessagePropDefName,
     DataType = MFDataType.MFDatatypeMultiLineText,
     ContentType = MFContentType.MFContentTypeGeneric,
     ObjectType = logObjectTypeID, // Either ID of the newly created ObjectType or the found-by-alias ObjectType
     BasedOnValueList = false,
     AllObjectTypes = false,
     Predefined = false,
     ObjectsSearchableByThisProperty = false,
     HistoryVersionsSearchableByThisProperty = false,
     AllowedAsGroupingLevel = false,
     SortAscending = true,
     FormattingType = MFFormattingType.MFFormattingTypeNone,
     AutomaticValueType = MFAutomaticValueType.MFAutomaticValueTypeNone,
     ValidationType = MFValidationType.MFValidationTypeNone,
     UpdateType = MFUpdateType.MFUpdateTypeNormal,
     AccessControlList = new AccessControlList(),
   };

   var propDefAdmin = new PropertyDefAdmin()
   {
     PropertyDef = propDef,
     SemanticAliases = new SemanticAliases() { Value = "PD.LogMessage" }
   };

   var newPropertyDefAdmin = vault.PropertyDefOperations.AddPropertyDefAdmin(propDefAdmin);
   logMessagePropDefID = newPropertyDefAdmin.PropertyDef.ID;
 }


 // Add Class if it doesn't exist
 if (logClassID == -1)
 {
   var associatedNamePropDef = new AssociatedPropertyDef
   {
     PropertyDef = 0, // NameOrTitle
     Required = true
   };

   var associatedLogMessagePropDef = new AssociatedPropertyDef
   {
     PropertyDef = logMessagePropDefID,
     Required = false
   };

   var associatedPropDefs = new AssociatedPropertyDefs();
   associatedPropDefs.Add(-1, associatedNamePropDef);
   associatedPropDefs.Add(-1, associatedLogMessagePropDef);

   var objectClassAdmin = new ObjectClassAdmin
   {
     Name = structureConfig.LogClassName,
     ObjectType = logObjectTypeID,
     NamePropertyDef = 0, // NameOrTitle PropertyDef
     AssociatedPropertyDefs = associatedPropDefs,
     ForceWorkflow = false,

     SemanticAliases = new SemanticAliases() { Value = "CL.Log" }
   };

  var newClassAdmin = vault.ClassOperations.AddObjectClassAdmin(objectClassAdmin);
  logClassID = newClassAdmin.ID;
}