On:
http://schema.org/WebPage

We find this example (quoted is the "Without markup" tab)

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by John Doe
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However, the class schema.org/WebPage is not employed in any of the examples: not in the microdata, RDFa or JSON-LD tabs. The only class employed is schema.org/Article (and the only relation that Article has to WebPage is that they're both types of CreativeWork).

Accordingly, this example should either be changed to use WebPage, or removed. The only likely consequence of using an "example" for WebPage that does not include WebPage is to confuse users that look at the example.