Why is What is the difference between slice, segment and leg? on-topic while What are the definitions of stages and sequences when describing a flight, and how do they compare against leg/portion/sector/segment? [closed] was closed as off-topic?
As is so often the case in these sort of meta-questions ("Why is X on topic but Y not?") you're comparing a very old question (left open, possibly on topic in it's day) to a very new question (closed, as currently not in scope).
If the open question were asked today, I would expect it to be closed for the same reason the now closed one is; our scope has moved on, and questions about the "passenger aspects" of aviation are specifically off-topic.