Error in required structured data element - Is Google AMP biased towards a set of use cases?

Recently I have added Google AMP (accelerated mobile pages) support for my blog articles, but I am observing following error in google Webmasters search console -

Error in required structured data element
Fix the structured data element in your page. AMP pages with an invalid required structured data element may appear in Google Search results without AMP-specific display features

This problem is happening as I am missing a subset of required schema.org structured data elements to be included in the head. More specifically my amp pages are missing following required fields - image, image.url, image.height and image.width.

As per google article specification, "image" is defined as

The representative image of the article. Only a marked-up image that directly belongs to the article should be specified.

Because most of my blog articles are just text, I don't have a representative image of the article. I have seen people faking it by including a fixed image for all amp articles (e.g., most of wordpress blogs with amp support), but that seems to be against the specification of "Only a marked-up image that directly belongs to the article should be specified."

Ideally Google should declare image elements as optional.