Split input lanes are useful to limit chest insertion when the lanes contain different items.

Not possible to do because of Factorio game engine limitations on inserters. An inserter cannot be told to pickup from only one side or the other of a belt.

Oh, right! Still, it would work with filter miniloaders. But I guess it destroys the illusion of loaders if the filters are configured wrong.

It would not work with filter miniloaders. You can’t meaningfully configure the two lanes to be different, because the inserters will pick up items that match their filters no matter what lane they are in.

The filters could match the insert condition and what's (supposed to be) on the respective lane. But as I said, that configuration requires implementation knowledge that miniloaders actually are two inserters.