In Factorio 1.1 you used to be able to reach higher unloading speeds outputting into a splitter which acted like placing items on two belts at once. This is no longer the case after Factorio 2.0 with the exception of green splitters. Read the forum if you want to know more. You can also watch the AVADII's video about the topic.

This mod is only a dirty hack to bring that behavior back. I see no way to change the actual splitter mechanics so all splitters are converted to the parameters of turbo ones under the hood. This can be exploited if you really want to but the benefits are kind of trivial so it's not a big deal.

No hacks needed now! The mod modifies the inserter's item drop location instead. So simple it feels vanilla! Also, in case you wondered - placing items above the input of a splitter in 2.0+ already works the same way as dropping them from the side did before 2.0. Why the devs think it is ok here - who knows!