That's a brilliant article, the most detailed summary of this whole fascinating episode I've ever seen.
The general suggestion is that the Christmas Pops from 1978 is so bad because it had to be flung together quickly after the strike, but I don't think that's the case. Although they use the office set, it is clearly a set, and those visual gags must have taken a bit of time to set up (plus the special message from Abba, of course). A lot of the performances are new as well - the Darts one certainly is, because Kenny Andrews is in it, who wasn't in the band when the record was a hit. There isn't an audience, but there generally wasn't one for Christmas shows in those days - 1976 is the only year between 1974 and 1980 there was one - and you can compare it to the show from the previous year which has about the same number of new performances and, as I say, no audience, the only real difference is that it's on the familiar Pops set. We expect the Christmas show these days to be a very glamorous production but in those days it was often the least glamorous show of the year.
One thing that had always puzzled me, though, is the Pops from 21st December, because as Genome points out, it was going to be an hour long and was ostensibly "part one" of the Christmas show - https://genome.ch.bbc.co.uk/schedules/bbcone/london/1978-12-21#at-19.25.
You would assume if that was the case, they would have started work on that a bit sooner than the previous day, so I wonder if anything intended for that actually exists. Bit of a shame it was never finished, would have been a bit better than the awful show we did get.