How to programatically fetch the latest versions

I found this thread today while looking into how to keep op up to date with Renovate. Thanks for documenting the update-check endpoint here (.../check/1/0/CLI2/en/2000001/N). I'm using it to track op with Renovate, and it is working fine. I'd like to add a few gaps I ran into, in case this request can be revisited.

What is missing for dependency-update tools

• Only the latest version is returned. A tool can't offer the newest release within an older major, or see what was skipped.
• No release date. Renovate's minimumReleaseAge (a cooldown before adopting a new release) can't be applied, so I have to exempt op from it.
• The endpoint isn't in the official docs, so I don't know whether it is a supported interface for third-party tools or if it is stable.

I also found release RSS. It has versions and dates, which is what I need. But Renovate's custom datasources can’t parse XML (it can parse only JSON, YAML, TOML, HTML and plain text). Using the feed means extracting items from raw XML with regular expressions and converting RFC 822 dates to ISO 8601 in a template, which is fragile.