In the editor, a directory scan filtered on .tres finds the item files and loads them; in the exported APK the same files exist only as .tres.remap stubs pointing into .godot/exported/, so the filter keeps zero files and the game gets empty data without any error.
Godot

Godot 4 export turns every .tres into a .tres.remap stub, so a DirAccess scan filtered on .tres finds nothing

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On export Godot 4 converts .tres to binary and leaves .tres.remap stubs; a directory scan filtering on ‘.tres’ loads zero files in the APK, with no error.