AMP and canonical pages required to match
Though AMP isn't a ranking signal, non-compliant pages won't appear in Top Stories or other AMP-specific slots in search results.
Google has said that beginning in February 2018, Accelerated Mobile Pages (AMP) and canonical pages must match or have very “close parity.” AMP pages that do not match the content of canonical pages “will not be considered for Search features that require AMP, such as the Top Stories carousel with AMP.”
read original story here
Google is doing this because it is seeing AMP used, in some limited contexts, on “teaser pages” that offer only limited content. Google uses the example of a news article whose AMP page features an excerpt with a prompt to click for the “full story.” In such cases, users are being required to “click twice to get to the real content.”
If Google finds a non-compliant AMP page after the deadline, it will send users to the “non-AMP equivalent.” If that’s a slow-loading page, users are likely to abandon.
Google says it’s doing this to promote a better user experience. It’s also seeking to protect the integrity of the AMP initiative itself.