The short version
In the context of BIAB – the free Sforzando replaces the free Sampletank2 for use for by PG BIAB Hi-Q sounds, and Sforzando program uses files of the format .sfz: Sforzando does NOT use SampleTank file formats.
The slightly longer version
Sforzando is a FREE soundfont player – could have downloaded anytime you wanted –didn’t need PG via BIAB to give it to you. For the most part soundfonts come in two formats .SF2 and .SFZ - .sfz being a more robust format (and actually human editable – if you know what you are doing). Soundfonts go back to SOUNDBLASTER sound card days
You can google Sforzando, soundfonts, .sfz’s and .sf2’s etc.
Btu here is one to get you started
https://en.wikipedia.org/wiki/SoundFont