I too hate it when vendors put textures and object files in library folders. Some vendors have done so for years and now they have content in P8. 

I've spent considerable time debugging how Poser search behaves when clicking a library file (looking at the actual search pattern, not the original source code). I posted an example experiment of the search pattern some months ago, if anyone is actually interested. Here it is. Results were one of the reasons I dropped using external Runtimes altogether and now using only a single main Runtime.

It can be argued that Poser eventually finds a file that is incorrectly referenced (if it exists within the Runtime, that is). In a "test" Poser setup with minimal content everything looks just fine.  However, many people have content libraries (multiple Runtimes or not) exceeding 100Gb with thousands of folders and literally hundreds of thousands of files. A missing reference search will always go through all of that and it can not be even stopped within Poser. Letting the vendors publish their stuff with incorrect references casts a very negative light on the overall quality control of SM.