This doesn't refer to your pictures but has a general explantion. Emphasis added by me.
Tuner wrote: "The difference is the larger holes in the well tubes make for bigger bubbles in the nozzle stream and that tends to make the fuel discharge in larger globs instead of a smooth flow.
A tube similar to the one with large holes under the 340 was used in some Pontiac AFBs
but they only had .026” in the main air bleed tube and also had a fairly large surface in the exhaust heat exchange area in the floor of the plenum. On the other hand, some Chevrolet AFBs had tubes with no holes at all except for a kill bleed above float level. Many AFBs of all OE manufacturers had no tube in the secondary cluster. Remember, in AFBs the air comes into the well outside the tube and exits the well up the tube with the fuel."
One takeaway is the large holes will work best with a heated intake manifold floor.