That might depend on the specific Safari version. I am using Safari 10 on macOS Sierra, and it would not allow me to access any site using one of the affected certs: instead it would just serve an error page.
I think that was more because of the site, not the certificate - the grey failure page would appear for sites that use HSTS[0]. If the site didn't use HSTS or if you visited it for the first time, you'd get an ordinary certificate error alert.
