I am pretty sure that "Last Knight" is the most traumatic series finale of any show ever. *g* At least, if there is one that was more egregious about stomping on its fan's hearts, I can't think of one ...

And aha, that would explain some of the season/air date stuff that I had wondered about. They've got those episodes included with the season four DVDs (probably in the order that they were originally intended to air) but some episode guides list "One Minute to Midnight" as the season five opener.