different, alternative .kext location

Why is there another prominent location used for kext files ?

Besides the main location /System/Library/Extensions there is also this one that doesn't sit in the main systems folder : /Library/Extensions

I've encountered an extension brought in with my P2 plugins for FCPX that lives in both locations, being the exact same file, the version and date are identical.

But the one in the "official" location is brandmarked as "not signed" while the one in the "alternative" location has the correct signature and Panasonics develpper ID. ( the same occurs for two other P2 related extensions, that group is the only one to have duplicates in both worlds )

Other inhabitants of the /Library location are sourced from Blackmagic Design drivers and CalDigits Thunderbolt 2 Station utility.

Those last elements in my work environment are functioning without problems, so these extensions seem to be active in the same way the "official" ones are.

Beside safeguarding my main drive with Time Machine, I also do a daily CCC incremental backup. At the end of the procedure, CCC signals me everytime this unsigned extension as a "reminder", this file being nonetheless loaded at startup, my P2 ingests performing normally.

Does anyone know about the justification of this second location, even closer to the root ? Any opinions about some sort of prevalence of one file agains the other ?