Hello and welcome to our forums,
All MSIX packages have a predefined install location where the OS extracts the resources, the location being:
As you have mentioned, this is a system location that, by default, is inaccessible from Windows Explorer.
For more information about this, please have a look over the following:
MSIX - Install Location
Even though the files are installed in %programfiles%, the MSIX is actually installed per-user, not per-machine
For more information about this, please have a look over the following article:
AppData Management in MSI/MSIX/APPV
Hope this will help shed some light over this topic.