This is the quote I meant to respond to. Why is that appropriate?
I don’t know. I didn’t do it.
Seriously - I think the idea behind it is that the Judaeo-Christian tradition has had such major significance on the western world that dividing dates into the pre-Christian and post-Christian eras makes a great deal of sense.
This is not as true for other areas around the world - but when we look at their histories, we often still find a useful ‘dividing date’ somewhere approximately around AD1 - for example, with China, the Han Dynasty encompasses around -200 to +200 (yet another dating system!), with Japan, the Yayoi period frames -300 to +250, in India, the Middle Kingdoms arise about that time... there’s a decent case to argue that the world in general changed at that time, and so as a convenient dividing date, the Gregorian calendar is still useful - but using BC/AD would put risk ignoring the reasons the changes occurred.
Personally I do use BC/AD in my classes and differentiate where necessary by using references like, “During the Qin period,” but I’m also aware of the discussion that goes on around these issues, and it makes me wonder if the mover back to BC/AD in some US contexts might come from this ‘compromise’ rather than a return to the older principles.