See microsoft#885 (comment)

Author: jrandolf

baselines/dom.generated.d.ts

@@ -4770,7 +4770,7 @@ interface Document extends Node, DocumentAndElementEventHandlers, DocumentOrShad
      * Gets a collection of objects based on the value of the NAME or ID attribute.
      * @param elementName Gets a collection of objects based on the value of the NAME or ID attribute.
      */
-    getElementsByName<E extends Element = Element>(elementName: string): NodeListOf<E>;
+    getElementsByName(elementName: string): NodeListOf<HTMLElement>;
     /**
      * Retrieves a collection of objects based on the specified element name.
      * @param name Specifies the name of an element.

inputfiles/overridingTypes.json

@@ -567,7 +567,7 @@
                         "getElementsByName": {
                             "name": "getElementsByName",
                             "override-signatures": [
-                                "getElementsByName<E extends Element = Element>(elementName: string): NodeListOf<E>"
+                                "getElementsByName(elementName: string): NodeListOf<HTMLElement>"
                             ]
                         },
                         "createTreeWalker": {