Google Video Snippets Showing Different Web Sites?

Joost de Valk from Yoast SEO, who has a wealth of access to tons of SEO data, asked Google on Twitter "did Google roll out a change in video snippets? We're seeing video card and snippets in the normal search results for loads of sites that didn't have them a while ago." Google did not respond but the tracking tools do show some fluctuations in the video boxes.