My team is successfully using it to track ~200k issues/PRs across ~300 repos. We wrapped our deployment in a minimal API to give our infra blazing fast access to that data without needing to worry about GitHub auth or rate limits (since Maintner handles that).
And, we use the proxy described in the article.
Of course, in your case, it might be debatable in terms of utility - if you're trying to replace a scan, you probably are trying to get results as "up to date" as you can - which would be prevented if the cache avoided doing that! The cache would have the same rate limits, and so you would be just as well off adjusting the frequency you currently scan. Of course, if you can't control that frequency (perhaps multiple uncoordinated scanners) a proxy is one way to give you that control - so maybe useful!