BrowserSync does not call router with grunt-php when reload

[simongcc]

I am using grunt-browser-sync with grunt-php.
Since I have put the css files in a temporary folder .tmp outside app folder during development, so I am using a router to load the css files. When it is first run, php is started and then BrowserSync monitor changes. When css changes is detected, it reload. However, because the path of .tmp does not exist to the php file, router need to be called in order to load the css file correctly.
In this case, BrowserSync seems not call the router and just reload the page normally.

I think it is a feature or enhancement rather than bug. If there is any other way or better way to make use of .tmp folder are welcomed to suggest.

Many thanks.

Updated 2017-05-05
To illustrate the problem, I have created a demo and put in the git, please visit and fork a version to test: grunt-browser-sync-demo