The issue is the difference between General Midi (GM) and full Midi.

Biab runs on GM because it doesn't require any understanding of the very cryptic details of midi. GM only provides limited control over midi instruments. Volume, expression, velocity, a few more. You can use Kontakt just fine in biab, you will hear the instruments but all the realistic articulations you hear in their demos require the use of non GM controls. This is why Biab won't sound as good as the demos you hear of the excellent Kontakt instruments. It has to be used in a DAW that uses all the midi controls and the user needs to be proficient with midi.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.