[Exim] "freeze" in system filter & auto-thaw

I've just been editing the system filter on my Exim (version 3.34) server
as a reaction to a serious attack of the Sobig virus. The "freeze" command
is now executed for all messages that seem to match the filter.

Question:

From the Exim spec,

... freeze suspends all delivery attempts. It is ignored if the message
has been manually unfrozen and not manually frozen since. This means that
automatic freezing by a system filter can be used as a way of checking out
suspicious messages. If a message is found to be all right, manually
unfreezing it allows it to be delivered.
Am I correct in interpreting the word "manually" as meaning that the note
in the last line does not apply to the unfreeze caused by

auto_thaw = 3d

also present in the config? In other words, I'm assuming that messages
frozen by the filter will *not* be delivered when they are *automatically*
unfrozen for a 2nd delivery attempt 3 days later. Is this correct?

--
- Toralf