First of all: I strongly recommend to update your installer version (it is 0.15.9 in your case, thus far beyond the current version).
This said obsidian does not (yet) insert an alias if the file you link to is located in the same directory as the note you are linking from. This is default behavior so far, thus no bug.
I am quite certain (couldn’t find it quickly) that there is at least one open feature request for creating a new note in a different folder by clicking an unresolved link that contains a file path (like [[path/to/subfolder/my-new-note]]
- I think this is somehow related to your problem.
Edit: even more related is this feature request: