Google’s John Muller clarified on Twitter that before moving a site from desktop-first indexing to mobile-first indexing, Google would want to see the links on the desktop version and compare it to the mobile version. If those links in the content and source code of the pages are not equivalent enough, it might be suspected not to have yet moved over to mobile-first indexing.
It is known that Google has begun the process of rolling out the mobile-first indexing which is currently putting many SEOS and webmasters nervous. To clear their concerns, Google keeps on telling them not to worry about that.
Look at the discussion at Twitter:
According to John, they do check things like links before switching sites over. So, there’s no need to get worried, because, if you have not sufficient links on mobile, then you have to fix that problem first.
Make sure your mobile and desktop pages stay equivalent what Google is stressing on for quite some time.