From the launchctl(1) manual:
asuser UID command [args]
This executes the given command in as similar an execution context as possible to that of the target user's bootstrap. Adopted attributes include the Mach bootstrap namespace, exception server and security audit session. It does not modify the process' credentials (UID, GID, etc.) or adopt any user-specific environment variables. It affects only the Mach boot-
strap context and directly- related attributes.
This might be the reason for https://gitea.pep.foundation/pEp.foundation/pEp4Thunderbird_PublicBugTracking/issues/2#issue-24