Tomo from Google said in an ongoing Google Webmaster Help thread about disabling AMP in search that last week Google released a way for iOS users to scroll away the AMP top bar.
Tomo said this on January 6th:
A quick update to say that the Search team has pushed a fix for iOS that enables the AMP top bar to scroll away in Chrome and Safari. Please let me know if you see any issues.
The team is also still working on creating a direct path from AMP pages on Google Search to the canonical URL as specified by the publisher (usually the non-AMP original URL) and URL sharing functionality.
Please keep your feedback coming!
I tried to to do this myself but can't get the AMP top bar to scroll away in Safari on my iOS device. Clearly I am missing something. If you now how to replicate this, please share it in the comments.
Forum discussion at Google Webmaster Help.