NSD Device Lost Message Not Received on Disabling Wifi

Question

I have written a sample app using NSD as explained here.

The app works fine, it discovers services, resolve services and also report services lost if that service is unregistered.

But in a user scenario like:

1. If NSD app is running on a device named A and has registered a service on A
2. while few other devices named B, C, D are listening to this service.
3. service is discovered by B, C, D - expected behavior
4. now wifi is switched off an device A.
5. I am expecting to receive a service lost message on devices B, C, D, but I am not getting it?

If I do not switch off wifi on A, but just close the NSD app that unregisters the running service, I receive the service lost message on devices B, C, D.

What could be the reason for this? Is this a known bug with NSD? Or this is the way NSD behaves?