My insights are up to date, yet when I filter my correspondence games it shows me as having played just eleven games:
en.lichess.org/insights/cb99/result/color/variant:correspondenceNot much more to say really.
Yeah, the insights feature doesn't use all of your games. That would take way too much computation- it would overload the servers. Instead, they take a random sample of your games.
#2 isn't accurate. The games need to have computer analysis. Go analyse some your games then update insights.