To quote Pooh ha-Dov: "Oh, bother."Next question is why Luke would use such a construction here, which clearly seems intended and of which Nolland says, "... it is difficult to see Luke using the third person plural in place of the passive.." (WBC, Luke V 2, pg 687)
Part of the problem is that NT scholarship is often working from an incorrect paradigm, an out-of-date worldview. (Note the quotation of BDF above "influence of Aramaic" that only mentions 'Aramaic' for possibly explaining the structure.)
Because Hebrew was relegated by the 19th century to marginal-use-only in most NT worldviews, it was not considered viable for understanding the gospels or early church statements like Papias "in a Hebrew language."
Without Hebrew, Luke's Hebraisms/semitisms became "artificial Septuagintalisms", even when they didn't occur in the LXX !
Consequently, comments like Nolland's arise.
The other side of the coin is that Luke is replete with Hebraisms and semitisms, despite generally trying to smooth these out. Yes, Luke smoothed out semitisms, he didn't systematically add them. (For a humorous example, imagine someone adding the Hebraism "added to send another servant" in the parable of the vineyard, but splitting the word order to put ετερον in front of the infinitive and δουλον afterwards! If inteneded to evoke a LXX-al style it is schizophrenic.)
I see the plural in Luke 12:20 as reflecting Luke's source and left in place by Luke because it didn't cross a threshhold that needed changing.
Now what is supposed to be building a new worldview for gospel scholars is the FACT that not one ancient Jewish story-parable is recorded in Aramaic, despite both Hebrew and Aramaic being widely used throughout rabbinic literature. All the Jewish story parables are in Hebrew.
All 456 of the parables connected to tannaitic (=early) period texts and rabbis are in Hebrew. (All the Amoraic story-parables, too, for that matter.) Yes, I am aware that this is a mispredication and contradiction to the assumptions that grace most encyclopedia and commentary material on the gospels.
But 'facts is facts'.
And Luke 12 is a parable.
That assumes a Hebrew background somewhere in the transmission.
Do reflections of this show up? Fine. No problem. .