what is VMware's definitive process to confirm the baselines have been updated to the latest available patches?
If you go to Lifecycle Manager → Baselines → Critical Host Patches (or whichever Baseline you are interested in) → Then sort by Release date, you can then see the latest patches that have been downloaded into that baseline.
Also check your update settings via Lifecycle Manager → Patch Downloads → Settings → Edit. Here you can confirm Automatic Downloads are enabled and how frequently it checks for updates. You can also check Lifecycle Manager → Patch Setup, and confirm that your VMware Download Sources are present and have a connectivity status of "Connected".
Provided your vCenter host is able to talk to the VMware download repositories, it will download patches automatically, and new updates will appear regularly, as and when they are available. Typically the most recent patches will be dated within the last 30 days. As long as what you are seeing ticks all those boxes. you're all good