Is the ! (exception) subscription filter ?
When i look up this documentation nothing is mentioned about excluding specific topics from subscription by using "!":
(i would have expected a hint that this exists under certain conditions)
When i look here it mentions the possibility to exclude a topic by using ! in front:
So from what i read is likely not mentioned as it does not work in all cases.
Is that assumption correct ? Additional you have to enable to use that capability.
As well i assume you can only exclude or include the entire topic:
order/AP/*/CUST => all customer orders in region asia pasific
!order/AP/CN/CUST => exclude chinese orders from region AP
Problem with that is that as not everywhere supported in case of not being able to use the only alternative would be to list any country in region asia pacific except of CN.
That will add administrative complexity.