I think one of these 3 solutions should be implemented for all belt tiers consistently:

1) Either all splitter tiers should behave like the turbo splitter, 2x throughput and both output lanes saturated like in 1.1
2) or behave like the fast splitter now, normal throughput and split action, just as ...

Yes it's indeed a duplicate.
But in the other post boskid says it's not a bug.

Well, i think it is because the behaviour of the 4 belt types is inconsistent and doesn't make sense.
There might be limitations what the current code can do - i understand - but the current solution isn't optimal to say ...

Factorio version 2.0.20

When an inserter is dropping items into a splitter it seems that normal, fast and express belts cannot be saturated.
This is different from version 1.1.
This problem doesn't occur when using turbo splitters.

Steps to reproduce:
Build a chest and a bulk stack inserter. Let ...