You are correct, that the installer is basically for Amplitube and Sforzando.
I am not a fan of Amplitube myself, and never really used it in BIAB, so I generally skip that on each release.
Having said that, I would highly suggest installing the Sforzando BIAB sound files if nothing else that's on that disk.
I would first recommend getting the newest version of Sforzando from the Plouge website (
https://www.plogue.com/products/sforzando.html).
Then I would install the package "/Audio & MIDI Plugins/Data/Sforzando/Install HiQ_Instruments.pkg" at the very minimum.
That will install a little over a Gig of very high quality sounds to use in Sforzando, a lot of which rival the internal instrument sounds found in Logic Pro.
I also find myself using the Sforzando AU (with the BIAB sounds) in Logic fairly often, so there is that too.
Sforzando also provides what PG calls the "Hi-Q" sounds for BIAB MIDI tracks.
This is basically Sforzando integrated into BIAB, for quickly selecting nicer sounding MIDI instruments from within the BIAB program (I do find myself using this feature fairly often too).
To make full use of the "Hi-Q" instruments, you will have to install the preset files found in the "/Audio & MIDI Plugins/Audio & MIDI Plugins Installer.pkg" install package.
Hopefully my longwinded explanation helped.
- Jay