You control that via 'embellishment'. The use of a minor 6th is common practice.

In fact if you were to try that a different way you throw in a Bbm7b5 which will give you a similar Dm6 sound. This adds colour to the arrangement, however if you do not want the software to add embellishments you can turn them off.

Judicial use of this feature can greatly enhance the sound, and is more easily controlled in the midi styles.

Many of the Jazz Realtracks were laid down by Oliver Gannon, you might want to google him and thus gain some understanding of where the software is going. My most common usage of the software at present is to use Oliver Gannon, Neil Swainson, and Terry Clark as the rest of my quartet, with Miles Black popping in and out if I grab a horn for a verse.

My band thus shreds a lot like the real thing, but I don't let the solo too much, unless I need a beer.

John Conley
Musica est vita