The Kanonenvogel had 6 rounds per pod, this is not even close to being open for debate.
Why not?
The number is still 6 per pod.
I have a few books giving 12 per gun, but the only one I would call "reliable" is
Waffen-Arsenal Bd 133: Deutsche Sturzkampfflugzeuge Ju-87 Ju 88 by Joachim Dressel & Manfred Griehl.
It presents a "Flugzeug-Baureihenübersicht Junkers Ju-87", date 19 August 1944 giving "Chef TLR Fl. (E-2)" as a source.
Ju-87 G-1 and G-2 are both listed as having 12 rounds per gun.
If that is true (and I have no reason to doubt that, as it's in line with Mr. Williamson's findings), I may also have found where some confusion might have come from:
The Flak 18 was loaded with 6-round clips
per tray
But as we can see on this picture, the cannon seems to have two trays, one left & right:

So this would give each cannon 2x6=12 rounds
I will see if I can dig up some more...