Question about early 337 fuel management

[YankeeClipper]

Having read Ernie's helpful overview of the system, I wanted to ask: is the reason that the electric pump prevails when there is air in the line from auxiliary starvation, and where the mechanical pump fails, that the electric pump is immersed in the main? In other words, the electric pump is "pushing" fuel, which is in ample supply from all around, where the mechanical is flailing as it tries to "pull" air from a starved line?