Why can the Mail.dat PQT file indicate 3-digit package/bundle level for pieces in less-than-full AADC trays (or for 5-digit pieces in a less-than-full 3-digit tray) using MailStream Plus

Product Affected: MailStream Plus™, all versions, all platforms
In a MailStream Plus™ (MSP) First-Class Letter mailing there was a less-than-full AADC tray.  

The Audit Trail showed 2 'groups' of mail in it:
                    P Destination   Copies  Bundle                                     Cumulative
     RS H-Tr 1      P 530   AADC       149  GRP...........75  GRP...........74                149

The Qualification report had:
Cont      Cont Cont  Cont   Grp/Bdl  O  -----------RATES-----------  Running
Number    Size Lvl   ZIP    Dest     F         AB       MB       SP     Total

1         1-Ft AADC  530    530                22                          22
                            531                30                          52
                            532                32                          84
                            549                65                         149

The Mail.dat PQT (PACKAGE QUANTITY RECORD) had these 5 records:
QDQD3ERB00000001000001530       F 0002200022             O           #
QDQD3ERB00000002000001531       F 0003000030             O           #
QDQD3ERB00000003000001532       F 0002300023             O           #
QDQD3ERB00000003000002532       F 0000900009             O           #
QDQD3ERB00000004000002549       F 0006500065             O           #

Positions 17-22 are the Package ID number.  So the first three records went into 'package' 1, and the last two records into 'package' 2.  
Positions 23-25 give the Package Destination.  So according to the PQT, Package 1 had mail to 530, 531, and 532 in it.  

The F's in position 33 usually indicate that the mail is in a 3-digit bundle.  But if Package 1 has mail to 530, 531, and 532 in it, how could it be an 'F' 3-digit package?

This was an Automation Letter mailing.  Automation Mail does not get prepared in actual bundles.  The USPS DMM (Domestic Mail Manual) 235 2.0 defines a bundle as "A bundle is a group of addressed pieces, for a presort destination, secured together as a unit."
Automation mail does not get prepared into those types of bundles, because the USPS does not want to have to remove bands and strapping before putting the mail onto their automated machines. 

Additionally per the USPS DMM, in 203-
"4.1 Definition of a Bundle
Mailers assemble pieces available for different presort destinations into groups. A bundle is a group of addressed pieces secured together as a unit. The term bundle does not apply to pieces grouped loose in trays." 
4.3 Preparing Bundles of Letters
"For mailings consisting entirely of card-size pieces and mail in less-than-full trays, mailers must secure bundles with rubber bands, elastic strapping, flat plastic strapping, or string. Elastic strapping must be approved by USPS Engineering."

So in less-than-full Automation trays, pieces have to be securely 'grouped'.  This is so they aren't loose in the tray and get flipped around or otherwise disorganized.  This is why the Audit Trail at the top of this article showed two 'groups' of mail.

In this type of mailing in less-than-full trays, MSP uses the Mail.dat PQT-1102 Field Code (Package Level) to keep the pieces to each 3-digit sequenced together, it does not indicate an actual physical 3-digit bundle.  This usage is accepted by the USPS's PostalOne!, and common 3rd-party Mail.dat applications/editors.
UPDATED:  June 10, 2019