Engineering here (!) - confirm point (4), the fuel nozzle has a spring loaded metering valve within it. Fuel will not flow to the primary nozzle until pressure exceeds 30psi (and to the secondary nozzle as well at pressures over 150psi). Boost pump pressure is nominally what, 4-10psi? Either way, not enough to open the primary nozzle flow.
Simples
- VFR