Google may be updating the cache version of the sites that have been moved over the mobile-first indexing to show the mobile version of the web site. As you know, Google fixed the long standing cache bug for sites that are now on mobile-first indexing.
Glenn Gabe spotted Overstock’s web site showing the mobile version in the cache now and posted a screen shot on Twitter:
That is shows the mobile version of the Overstock website. When I tried to replicate it, I saw the desktop version – so maybe it isn’t fully rolled out yet.
It does make 100% sense for Google to show the mobile version of the site in their cache after a site is moved to mobile-first indexing because that is the site Google indexed now.
I just do not personally see it yet but that can just be a data center thing and it may take some time.
Forum discussion at Twitter.