New one for me but I agree with your interpretation.
3300 Uses Microlite as pernode / DSU
The 3300 gets a dual FIM card 50001248
PN for Triple FIM is 50001856
MOL Article 06-5157-00011 says:
In Release 7.0 and up of the 3300 ICP, the Software Installer Tool is used to migrate the SX-2000 database. You still use the 3300 ICP Configuration Tool to backup the SX-2000 database. The Software Installer Tool is then used to restore the SX-2000 database file to the 3300 ICP.
For further information, please refer to the Software Installer Tool help files in SI tool release 7.0.1.5 of the 3300 ICP Release 7.0.9.5.
Also:
Also, for additional information, please refer to article ID 04-1000-00068 - Migration Procedure for the SX2000
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Occam's Razor - All things being equal, the simplest solution is the right one.