Hi @tom, haha really? We have been using them for couple of months now. They seems to work except for the cpp project which mostly works.
Below are a few badge links which shows the correct info. Or were we luckly? 
https://codecov.io/gh/symbol/symbol/branch/dev/graph/badge.svg?token=SSYYBMK0M7&flag=client-rest
https://codecov.io/gh/symbol/symbol/branch/dev/graph/badge.svg?token=SSYYBMK0M7&flag=sdk-python