High SpamAssassin scores but Subject not modified

[Stephen Lee]

I'm running MailScanner-4.14-9 with SpamAssassin-2.53 compiled from
source on a Trustix1.5/Exim3 box. I noticed that SOME spam, identified
as such by Spamassassin, are not tagged with {SPAM?}. Here's an example:

Subject: Plastic surgery IN A BOTTLE ...
Date: Sun, 13 Apr 2003 06:17:12 +0100
MIME-Version:  1.0
X-Priority:  1
X-MimeOLE:  Produced By Microsoft MimeOLE V5.00.2919.6700
X-MSMail-Priority:  High
X-Mailer:  Microsoft Outlook Express 5.00.2919.6700
Content-Transfer-Encoding:  quoted-printable
X-Spam-Level:  Spam-Level SSSSSSSSSSSSSSSSSS
X-Spam-Checker-Version:  SpamAssassin 2.52 (1.174.2.8-2003-03-24-exp)
X-Spam-Report:  ---- Start SpamAssassin results 18.60 points, 5
required; *  0.7 -- From: does not include a real name *  2.0 -- Sent
with 'X-Priority' set to high *  0.2 -- BODY: Only $$$ *  2.8 -- BODY:
Human Growth Hormone *  2.2 -- BODY: Talks about exercise with an
exclamation! *  0.3 -- RAW: Quoted-printable line longer than 76
characters *  2.0 -- Listed in Razor2, see http://razor.sf.net/ *  4.4
-- Message-Id is fake (in Outlook Express format) *  3.9 -- Recipient
list is sorted by address *  0.1 -- Asks you to click below ---- End of
SpamAssassin results
X-Spam-Flag:  YES
X-MailScanner-Information:  Please contact the ISP for more information
X-MailScanner:  Found to be clean
Content-Type: text/plain; charset=iso-8859-1

I have the following set:
Spam Modify Subject = yes
Spam Subject Text = {Spam?}
High Scoring Spam Modify Subject = yes
High Scoring Spam Subject Text = {Spam?}
Use SpamAssassin = yes

My procmail filter normally identifies spam by the tag in the Subject
header. Should procmail be looking for "X-Spam-Flag:  YES" instead?

Thanks,
Stephen