Author here, and that's exactly right! I think it was in my second or third month on the job.
And I really agree with your second point too! Without that in-person transfer of tribal knowledge, it would have taken me ages to learn the ropes well enough to take such a high-pressure high-stakes oncall.
in addition to being a good story about the site reliability, it's also a great lesson in the value of collaboration, mentorship, and having senior people around whom you can ask for help!