Hi jcm2016,
Which pattern is played in an Intro does not depend on which Main Variation has been selected before. But each of the 15 style sections (Intro 1-3, Main Variation A-D, Fill-in A-D, Break, Ending 1-3) can be programmed to play different patterns depending on the chord being played.
This assignment is defined in the so-called CASM data (control data) of the style. There it could be specified, for example, that the bass pattern of MIDI channel 11 (of the style) is played for a major chord, but the pattern of channel 3 for a minor chord (for the current style section).
Hope this helps!
Best regards,
Chris