Is there any downside for using AMP JS components for none-amp page?

Question

None AMP page with any amp's component works as AMP page with any AMP component. I don't see any downside as long as I don't use Google cache component. Or is there?

Answer 1

AFAIK, yes there is. As mentioned in the documentation,

Google AMP Cache comes with a built-in validation system which confirms that the page is guaranteed to work, and that it doesn't depend on external resources. The validation system runs a series of assertions confirming the page’s markup meets the AMP HTML specification.

You may want to visit these links for additional insights and more information:

• OPINION - Implementing Accelerated Mobile Pages (AMP)
• AMP Project Website

Answer 2

There isn't really any downside. You can just use AMP as a web components library.

Note that there isn't a "Google cache component". HTML pages that pass the AMP Validator will be automatically served by the Google cache.