WiFi has no internet access...But it does!
"Connected, no internet access" means that the test that Android uses to check if there is Internet access is failing. The url or method used to test if Internet is working varies by Android version and on 6.0 it uses connectivitycheck.gstatic.com/generate_204 as the test. - Reference

"Internet" is just a network, if the routing, access, DNS resolution, etc. pieces are all there, the "Internet" is going to work... regardless if the test Android does to see if it is working fails or not, although you may have to specifically tell your device (via a pop-up toast prompt or setting in WiFi - Advanced) to stay connected to that WiFi network.

Why the test fails? Hard to say, but something in your friends network or their ISP is blocking the check your device makes to test if the Internet is working.