The hope was I would be able to get the local status of specific folders on demand via the GET request. So far I have not been able to find a method to filter the request to specific folder ids.
I was looking at the source and found reference to the GET /rest/db/completion which allows for specific folders to be specified. I did a quick test and it appears to be what I want.
I am not sure if there are advantages/disadvantages to using the GET against the events compared to against the db/completion.
At least in previous versions /rest/db/completion needed a lot of time depending on folder size so using it often was not a good idea, I think nowadays this is a lot better.
Events still has the advantage that you can continuously poll it (and it will block if there is no new event) to get instant updates for everything. I guess what is better depends on your usecase.