I'm afraid this would be controlled by Google. Once the meta description in Online Store Preferences has changed and saved, it will take Google some time to recrawl your site to take the changes into account. After you've already manually updated your sitemap and resubmitted the results, it will be up to Google to push these updates through. So there is nothing more to be done on your end, just to wait for Google.
I wish there were more we could do here to push it through! I'm sure Google will update these changes soon.
Let me know when you have an update!
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