Hoppers placed using /fill or /setblock with the tag "["facing_direction"=1]" get placed without a spout whereas hoppers placed with anyother value for "facing_direction" or by hand do. By testing this theory, I figured that for hoppers, if placed with "facing_direction" set to 1, it attempts to place the hopper supposedly with its spout facing up. I'd imagine the way to fix this is by changing the "facing_direction" variables for hoppers from numbers 0 through 5 to north, east, south, west, and down.
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This has been reported before at MCPE-62416, but the report was abandoned.
The "facing_direction" numbers now might be standardized to the same directions for any block that has a facing direction. That could make this working as intended.