In the meantime, I would put this on the same level as, say, changing the District Convention from 8-9 days to only 3-4.
I'd say it was more significant than that.
In the example you give, the conventions weren't changed, they were simply shorter; just as if they had been increased to say 10 days, it wouldn't have changed them.
However, with this the current change, a whole meeting is being removed. Yes, "they" can say that it's having its location changed but we all know that's just window dressing. No, the group study is being dispensed with, as the "Society's"™ own letter apparently states, so as "not to burden the brothers" in these difficult times.