[exim] Options that do or not affect trusted_users?

Sorry if this is a stupid question, but I just want to check that I
understand the docs correctly.

The way I read the specification (e.g. Sec.43.16), (1) these options

local_sender_retain
local_from_check
suppress_local_fixups

affect only messages sent locally by untrusted users; (2) a user is
"untrusted" if and only if he is not in trusted_users and he is not a
member of a group in trusted_groups; and (3) a trusted user's local
messages are never subjected to Sender-overwriting and the local-From
test.

Right? If wrong, how wrong?

Thanks.