Well, one of the things Arrangers do well (perhaps a defining feature), is "Auto Bass Chord." Even the lowly PSR-E463 has this. However its ability to accept an appropriate custom style is limited, and the bass is always the root of the chord.
An Organ has three sections- melody, harmony, and a pedal division for bass. It takes years of training to play a church organ well. But you can fake it convincingly using an arranger because when you play LH chords with accompaniment enabled you are in effect playing both harmony (the pad sound) and Bass. Add intelligent chord recognition, and when you press one or two keys, you're getting four or five notes in two different voices! It's a musical force multiplier!! That's exactly what I meant by my comment about the instrument being "approachable for novices on those weekends when the pros are out of town." IMO it would take real skill (and maybe a plug in manual and pedalboard) to achieve a complete church organ ensemble on something like a Hammond XK or stage piano.