You just went one step further than I did, and it is good information, thank you.
It seems the carb works like this:
The regulating needle is adjusted to full throttle as usual.
when the valve closes, the vacuum over the idle jets increases, and fuel draw would be too high for the limited amount of air that is admitted to the engine. This can only partly be compensated for by the idle jet sizes, so: This is compensated by air being drawn through the high jet, thus feeding the idle jets with a mixture of fuel/air. (supposing the main jet has no check valve)
Extra compensation is done by limiting the amount of closing of the throttle valve. (the bleed holes you closed)

This would probably work well for one engine only, so a different engine would need a new carb type (new number, different jet sizes and bleed holes).