If items are put into a hopper chain via directly in a hopper, those items will be equally split between the hopper below and the container the hopper is facing. ie failing to abide by hopper directional priority
Environment
Java edition vanilla
Windows 10
tested both in single-player and vanilla 1.16.3 server
This appears to be a duplicate of MC-149940, which was later resolved as, "Works As Intended".