Noted in https://phabricator.services.mozilla.com/D54747#1694131 there was a time where having the strings directly in github was necessary as they were used as part of prerendering, but that dependency was removed as part of bug 1555393. Now the duplicate files in browser/locales and browser/components/newtab/locales-src is a source of confusion and additional work to keep them in sync.
Bug 1601039 Comment 0 Edit History
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Noted in https://phabricator.services.mozilla.com/D54747#1694131 there was a time where having the strings directly in github was necessary as they were used as part of prerendering, but that dependency was removed as part of bug 1485002. Now the duplicate files in browser/locales and browser/components/newtab/locales-src is a source of confusion and additional work to keep them in sync.