I've seen websites that, by looking in their source, don't have any twitter:* meta tags like:
<meta name="twitter:card" content="summary" />
<meta name="twitter:image" content="https://farm6.staticflickr.com/5510/14338202952_93595258ff_z.jpg" />
but that still appear with a Twitter card when sharing the URL on Twitter.
They had og:image meta tags, so I thought that a page that has Opengraph tags: og:image, og:title, etc. would automatically be rendered with a card on Twitter. But after testing, it seems that no.
Question: is there a Twitter feature that makes that a page with no Twitter-specific meta tags, but Opengraph tags will be rendered automatically with a summary or summary_large_image card?