I think if your understood what I was saying you wouldn't think I was trying to convince you that Fmaj7/A is really an Amaddb6 chord. Believe me I am not trying to, and your point is correct. Even better your labeling the chord based on what you hear rather than the theory. I would probably label it the same way, but behind that way is something a little more. I know you know this but think of what a cadence is. A cadence is a way to end a phrase, not just 5-1 or whatever. You say you need more and I'm trying to give you that. Think the phrase as being in A minor and play those two chords as a cadence. Whether you call the second chord Amaddb6 or Fmaj7/A is pointless and to argue about it is folly. The point is it can signify an end to a phrase in A minor. What is beautiful about this movement is the psychological effect it has on the listener. Instead of the tension of the E7(b13) chord being resolved, it is continued on the Fmaj7/A chord. Leaving the listener with a sense of suspense and unresolved, which brings us to the C major chord next. Although the idea is there are two different phrases, the first in A minor which ends with E7(b13) to Fmaj7/A. Then a new one begins in C major. Point is the C major is not the final resolve, but Fmaj7/E. Re-voiced and renamed as Amaddb6, to make sense of a A harmonic minor cadence. You had a point when you said it works as a turnaround or a transition, but it can also be used as a cadence with this effect. Just listen to it.

Here’s a chord progression where it will work. Am - Dmaj - Am - G7 - Am - Dmaj - E7(b13) - Amaddb6.