[exim] control = submission in the DATA ACL

I have a feeling I'm overlooking something obvious here, but if I use the
"control = submission" ACL modifier in the DATA ACL, it doesn't appear to
do anything. I can't see anything obvious

exim -bh shows:

>>> using ACL "acl_data"
>>> processing "accept"
>>> check control = submission
>>> accept: condition test succeeded
LOG: 1CRViY-0003si-Kl <= <> H=localhost (test) [127.0.0.1] P=smtp S=216
250 OK id=1CRViY-0003si-Kl

but if I then do this for a "real" SMTP session, the message doesn't get
fixed up. It works fine if I use it in the RCPT ACL. I can't see anything
obvious in either sections 38.11 or 44 of the manual indicating that it
doesn't work for the DATA ACL, though again I may be being blind.

Is there some architectural reason why it doesn't work in the DATA ACL, or
am I being silly? If the former, would it be worth documenting and/or
raising an error if you try to do it?


Tim