Given that these are all people looking for a job, it's not surprising that the "likes" appear to be slanted towards things that commonly show up in job postings.
No it's good, you don't want to be bait-and-switched. So many job ads now say "Haskell/OCaml/Erlang..." But they're actually Java shops. Better to put the warning up front.
They are hiring for the new system they are trying to develop, and supporting the legacy code they can't get rid of. They are always overoptimistic on how much time will be spent on new vs old.
Analyzing the main Stack Overflow site would be more useful. You go to Stack Overflow when something doesn't work.