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Google could ignore any given metadata when it wants and how it wants. Ive seen this nummerous times that a manual set title and description is being thrown overboard and google simply selects the content thats onpage in this case. Dont stare blind on it; make sure your content is relevant on which you wanted to be searched for in the first place. The rest will pretty much follow.

You're right that the best plan is likely to look at adding that content onto the mobile versions of the category page (though it's worth rolling out slowly and carefully if you can't split test because we have seen it be good or bad in different circumstances - see this whiteboard Friday for example). In theory, with mobile-first indexing, Google will be crawling your site with a mobile user agent, and so as long as you are treating googlebot the same as you treat other similar user agents, it should see the page exactly as you do when you visit with a mobile browser (or emulate mobile using chrome for example). There are various ways to check different parts of this: Check what is actually indexed - by viewing the cached version of the page and / or searching for unique text that only appears on a specific category page "in quotes" Check what google sees using the URL inspection tool in search console and selecting "view crawled page" Good luck - I hope that helps.