Why does my Moto X phone support mDNS but my Samsung Tablet does not?
The standard Android distribution (as of version 6.0) doesn’t support mDNS resolution nor announce it’s device name on mDNS yet. So it’s up the device manufacturer to add support.

I’ll investigate how much effort it would be to write a mDNS client for Android to announce a device name. Shouldn’t be too complicated, though mDNS resolution wouldn’t be possible for an app at the current API limitations.