Yes the SF2 files are the original ones !
64Mb of samples in this virtuoso box

You can see some of the secrets the bigs are using, like using sample rate between 24000 and 37000 Hz

The problem with the conversion to Yamahan is that when a sample is using by many sound presets, they are duplicated in the Yamaha. I don't know if many motif sounds can share the same audio sample