The partial capo does not produce true open tuning unless the strings are retuned. Instead it provides a special effect which many guitarist find interesting.
It's most popular use is to apply the capo at the 2nd fret from the bass side, skipping the bass string and covering strings 5-4-3. This emulates DADGAD tuning, but a step higher.
Another popular use is to apply the capo from treble side at the 2nd fret covering strings 5-4-3. This emulates an open A Chord.
There are probably other applications which can yield interesting sounds, experiment, discover and enjoy.