The 2 key sentences in the second link that you provided:
As I mentioned earlier, these files aren’t being indexed in the local search index, though. If you click on Start and type in indexing options, you’ll see that the mapped network drive location is not listed nor can it be added. Note: Technically speaking, the Windows client will not add a network location to the local search index. Instead, it will pass that search on to the server and the server will perform a search using its index.
So on the server, you need to add that folder to the local index, because it won't be included by default. Like C:\Data\Whatever.
On the client:
Now right-click on the network drive and click on Properties. At the bottom, make sure to check the Allow files on this drive to have contents indexed in addition to file properties.