Do you have a custom language defined for .UNI?
It does not seem to be natively recognized by SE.
It looked like you drew dependency diagrams.
SE is not showing dependencies, it is just showing lexical meaning.
In a .H file, #define defines a symbol. So the tag parser treats those #defines as defining the symbols. I don't think you can do anything about that (unless you write a macro to scan the tag file for various symbols, remove them, and replace them with a modified version of the symbol that better suits your needs -- but I don't think that will work well in practice).
If you have a custom language defined for .UNI files, make sure that it reports the #string symbol as a definition. In that case there will be two definitions (one from .UNI, one from .H) and <Ctrl+.> on the symbol is expected to pop up a dialog asking which definition you are looking for. When using <Ctrl+/> to find references it will pop up the dialog, but it can't tell them apart and will find all occurrences anyway (so why did it prompt? don't know). Except it might leave out the competing definition, I'm not sure.