This code:
in_array( $request->getFullRequestURL(), $requestTitle->getSquidURLs() )
is used to determine whether the current URL is cacheable. But for HTTPS views, getFullRequestURL() returns an HTTPS URL while getSquidURLs() returns an array of HTTP URLs, so the in_array() call will never return true and the request will never be considered cacheable.
This means cache misses from HTTPS users are never used to populate the cache :(