Functionally the DSLsplitter
and DSL filter are very similar. The first problem you run into when
using a filter as a splitter is that you have to kludge some method of
connecting the filter into the phone line, and working the "bypass"
around the filter for the DSL connection.
But the main problem with using a filter as a splitter for your whole
house is that the filters are designed with the expectation that they
will drive one or two telephone devices.
When wired as a splitter, all of the telephone line voltage and current
must pass through the filter to get to all the telephone devices in the
home. The higher current load, especially when all the telephones are
ringing, may be too much for the filter. It may saturate and cause
problems with the DSL signal or the phones inside, or it may burn out
entirely.