After some experimentation, it seems that all the previous restrictions still apply (i.e. the AUv3 has its own Documents folder, and the normal file commands still work only within the AUv3’s sandbox.)
So the only way to load content outside the sandbox (or the parent app’s resource bundle) is to trigger the native browser? This is fine, of course; I just want to make sure it’s the case, as it will affect how we do presets going forward. Currently I’m using the Security Group’s dedicated folder so both the AUv3 and Standalone can work from the same pool, and I’ve provided an “Import” command to copy the contents of the shared docs folder to the Security Group so the user can import non-factory content, but obviously doing all the presets in the main Documents would, in the patois of our company, Increase Shareholder Value. So I just want to make sure that’s still the only game in town.