There's nothing under an updraft carb to stream fuel onto. It literally hangs out the bottom of the engine, with nothing below it. I think the scenario you describe is exactly why updraft carbs are used on aviation units in the first place - that and allegedly they don't flood the engine, but I've proved that theory wrong many times.
I would think that EFI (TBI) would be able to operate upside down since it is under pressure, and no need for a fuel bowl to sit and gravity to work it's course such as an updraft carb would have.
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