The query used to get the users contributions apparently only includes repositories to which the user has recently contributed to.

{
  viewer {
    repositoriesContributedTo(first: 100, includeUserRepositories: false, contributionTypes: [COMMIT, PULL_REQUEST, REPOSITORY, PULL_REQUEST_REVIEW]) {
      nodes {
        nameWithOwner
      }
    }
  }
}

Tested via https://docs.github.com/en/free-pro-team@latest/graphql/overview/explorer

It appears that older contributions have to be queried seperately somehow, for example by scraping the users profile, by abusing the search api or via third party tools such as BigQuery: https://stackoverflow.com/a/63427144