Clarify in Body.json() doc that it returns a JS object, not JSON (#3098)

Co-authored-by: Michael[tm] Smith <mike@w3.org>

files/en-us/web/api/body/json/index.html

@@ -13,8 +13,10 @@
 <div>{{APIRef("Fetch API")}}</div>
 
 <p>The <strong><code>json()</code></strong> method of the {{DOMxRef("Body")}} mixin takes
-  a {{DOMxRef("Response")}} stream and reads it to completion. It returns a promise that
-  resolves with the result of parsing the body text as {{JSxRef("JSON")}}.</p>
+  a {{DOMxRef("Response")}} stream and reads it to completion. It returns a promise which
+  resolves with a JavaScript object that is the result of parsing the body text as {{JSxRef("JSON")}}.</p>
+
+<p>Note that despite the method being named <code>json()</code>, the result is not JSON but is instead the result of taking JSON as input and parsing it to produce a JavaScript object.</p>
 
 <h2 id="Syntax">Syntax</h2>