Thank you for your reply. The time to human level is simply the time it took between the initial release of the website to when an AI system reached human level performance for that benchmark. :) I am in the process of adding sources for all "solved" dates... Here is for instance source for the Winograd challenge human level performance:
https://arxiv.org/pdf/1907.10641#:~:text=The%20best%20state%...).
:)