[Exim] timeout_frozen_after

I have recently upgraded exim to 3.33 to be able to use
timeout_frozen_after. I have in my queue:

49d  2.4K 15Ru5s-0003cW-00 <> *** frozen ***
          someuser@somedomain

I have in my config:

ignore_errmsg_errors_after = 24h
timeout_frozen_after = 7d
auto_thaw = 1d

(amongst other things, but these seem to the be the most relevant)

Now we have had plenty of other messages this old on our queue which have
now been succesfully timed out after I set this option. However this one
is proving more stubborn. I'm curious about why I am seeing this variable
behaviour.

Full trace:

# /usr/local/bin/exim -d9 -M 15Ru5s-0003cW-00
Exim version 3.33 debug level 9 uid=0 gid=1
probably ndbm
Actual local interface address is 127.0.0.1 (lo0)
Actual local interface address is 154.15.247.42 (hme0)
Actual local interface address is 154.15.249.158 (hme0:1)
Actual local interface address is 154.15.250.158 (hme0:2)
Actual local interface address is 154.15.251.158 (hme0:3)
Actual local interface address is 154.15.252.158 (hme0:4)
Actual local interface address is 154.15.253.158 (hme0:5)
Actual local interface address is 154.15.254.158 (hme0:6)
Actual local interface address is 154.15.255.158 (hme0:7)
Caller is an admin user
Caller is a trusted user
set_process_info: 28223 delivering specified messages
delivering message 15Ru5s-0003cW-00
set_process_info: 28223 delivering 15Ru5s-0003cW-00
Opened spool file 15Ru5s-0003cW-00-H
user=root uid=0 gid=0 sender=
sender_fullhost = (someserver) [123.123.123.123]
sender_rcvhost = [123.123.123.123] (helo=someserver)
sender_local=0 resent=no ident=unset
Non-recipients:
Empty Tree
---- End of tree ----
recipients_count=1
body_linecount=50 message_linecount=16
LOG: 0 MAIN
Unfrozen by errmsg timer
Delivery address list:
someuser@somedomain
locked /var/spool/exim/db/retry.lockfile
opened DB file /var/spool/exim/db/retry: flags=0
>>>>>>>>>>>>>>>>>>>>>>>>
Considering: someuser@somedomain
somedomain in local_domains? no (end of list)
unique = someuser@somedomain
dbfn_read: key=R:somedomain
dbfn_read: key=R:someuser@somedomain
someuser@somedomain: queued for routing
>>>>>>>>>>>>>>>>>>>>>>>>

After directing:
  Local deliveries:
  Remote deliveries:
  Failed addresses:
  Addresses to be routed:
    someuser@somedomain
  Deferred addresses:

>>>>>>>>>>>>>>>>>>>>>>>>
routing someuser@somedomain, domain somedomain
lookuphost router called for someuser@somedomain
dns lookup: route_domain = somedomain
DNS lookup of mail.nl.redwoodsw.com (MX) succeeded
Actual local interface address is 127.0.0.1 (lo0)
Actual local interface address is 111.111.111.112 (hme0)
local host has lowest MX
fully qualified name = somedomain
host_find_bydns yield = HOST_FOUND_LOCAL (3); returned hosts:
mx1.mydomain 111.111.111.111 5000 500020
mx3.mydomain 111.111.111.113 5000 500079
mx2.mydomain 111.111.111.112 5000 500084
LOG: 0 MAIN
lowest numbered MX record points to local host: somedomain
lookuphost router: error for somedomain
message: lowest numbered MX record points to local host
post-process someuser@somedomain (8)
LOG: 0 MAIN
== someuser@somedomain R=lookuphost defer (-1): lowest
numbered MX record points to local host
search_tidyup called
set_process_info: 28223 tidying up after delivering 15Ru5s-0003cW-00
Processing retry items
Succeeded addresses:
Failed addresses:
Deferred addresses:
someuser@somedomain: no retry items
end of retry processing
LOG: 0 MAIN
Frozen
delivery deferred: update_spool=1 header_changed=0
Writing spool header file
Size of headers = 760
end delivery of 15Ru5s-0003cW-00
search_tidyup called
search_tidyup called