Just a general FYI on this topic - I just spent some time troubleshooting an issue with Sage and Vagrant (NOT Bedrock) where browser-sync appeared to be working but was not showing the correct injected CSS.
The answer was that Nginx on my Vagrant setup had the ‘sendfile’ setting set to ‘on’, setting it to ‘off’ in my nginx.conf immediately fixed the problem.
Hope this helps someone.