The app is doing an http(s?) request, which includes more round trips than a simple ping. Also, the web server may be more loaded than the ping response would indicate.
Usually not. I got a similar "ping" page on my website but haven't found a browser that closes the TLS connection between secondly requests. Also built a websocket version but that turned out to only be useful as canary because it doesn't survive connection changes.
Aachen|3 years ago