As per title...
After manually checking for updates (or when visiting the available updates page) you are informed of the time the last check occured, but you actually need to scroll through the whole list of modules and scan to check for any updates. So, unless you are comming from the status report page or there is a critical update (and thus a red warning about it), there is no other way to know by simply visiting the available updates page.
How about a 'Last checked: 2 sec ago - Updates found: 2 (1 of which is critical) (Check manually)' or something like that?
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.