I acknowledge that this is probably working as intended, and is probably the same behavior from 1.1 and much farther back, but I just discovered it today and it irks me, so...
There are 2 iron plates here that I expect to be in pickup range of these inserters. If the top half of the splitter was replaced with a belt with 2 iron plates and 2 sulfur on it, the splitters would be able to pick up the iron plates.
I know that an inserter can only drop on the "middle of the splitter" slot on a splitter, or the middle of the far side of a belt, but on a belt an inserter can pick up from the near and far corners of the belt, so I would expect that to work here as well.
[2.0.15] Inserter can't grab from input side of splitter
Re: [2.0.15] Inserter can't grab from input side of splitter
The amount of iron plate [not] obstructed by an underground seems to be the same* as for a splitter, and an inserter can grab that exposed plate on the underground.
* - the underground is a few pixels farther right, but the item on the belt is also a few pixels farther right