Sorry, I'll try to explain:
In Stella, there is a Ab9 that is really a Ebm6, making a plagal cadence, as
you have explained previously.
I've seen lots of reharmonisations where a V7 or a bII7 is substituted by a
m6 chord a 4th below:
G7(9) by Dm6
G7(b9,b13)=Db7(9) by Abm6
So my question is: is there some justification for this, or it just happens
these modes have the same notes (naturally, as both come from melodic minor
scale) and can be interchanged? :
Lidian b7: 1 9 3 #11 5 13 b7
Melodic: 11 5 6 7 1 9 b3
Pedro