Thats just how DirectShow works.
The one is a Source Filter, it reads files/streams directly and demuxes them. Not much else to it.
The other is a Splitter Filter, it gets the stream from another DirectShow source filter, and then demuxes it.
The Splitter Filter always needs another Filter to read the file or the stream for it. The most basic case is the "File Source (Async)" filter, which just reads files, but it could be a more advanced streaming filter or in theory even a Live TV Source (although that probably won't work right).
The first case (LAV as pure Source Filter) has a little less overhead, and for proper handling of streaming protocols its required to be used. Generally this is the better choice to use.
The second case (LAV only as Splitter Filter) has the advantage that it doesn't need to manually be hooked up to all sorts of file extensions, but instead most players will just load a "File Source (Async)" when no other Source Filter is found, which is then connected to LAV Splitter, and it can then probe the stream itself without relying on the file extension (identifying the format based on byte-markers in the file)
So, even in a properly setup system, both have their uses.
The LAV Installer will setup the Source Filter to be used for all common extensions, so that the slightly more efficient way is used, and register the Splitter Filter so that its available for all the other cases.
For comparison, Haali has the same setup.
Its "Source Filter" is just called Haali Media Splitter, and the "Splitter Filter" is called Haali Media Splitter (AR)
Just don't worry about it.
