I do not really believe that. I have a site which is served way faster than it's Amp version. Obviously Google never really care to check whether original page is faster than AMP. Yes I have numbers. AMP version loads about 400ms. While the original was about 300ms. Almost certain for all pages.
That was likely a singular measurement, likely from your notebook. A user at some other location might very much disagree, unless your site has a CDN as extensive as Google.
See also: https://www.theregister.co.uk/2017/05/19/open_source_insider...
"Pinboard founder Maciej Cegłowski already recreated the Google AMP demo page without the Google AMP JavaScript and, unsurprisingly, it's faster than Google's version."
Is it really that surprising that Google finds crawling pages stored on their own CDN to be faster than pages stored... anywhere else? They don't even need to leave the Google network.
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Unless you have solid evidence to the contrary, I see no reason to believe you over believing Google.