[embedding-shape]

Authors point is something like this:

Users expect that their ticket been successfully purchased when the gray "Buy" button turned "Green! Yay", this is "the system" or whatever they call it. Just because the request went to backend and returned 200 OK doesn't necessarily mean that everything after that successfully completed, maybe the payment webhook was badly configured, and so on.

It seems pretty clear to me that this is what the author means and are talking about. But I'm not entirely why they're talking about this, or if there is any further point beyond just the "technically correct but ultimately not important" part.

[cyclonereef]

It's the same sort of pedantry as correcting someone's use of their/there/they're. Yes, technically you're correct in what you're talking about, but arguing minutiae that is probably not relevant to the overall discussion.