4 diodes in parallel is for current, the current will, one hopes, divide between them more or less evenly.
No it doesn't reduce the diode drop to use more diodes in parallel (ignoring other conditions which affect the diode drop of diodes).
If the diodes are not well matched, then you may get into a situation where one or more of the diodes have a low enough forward voltage drop that they cause the other diodes to not be sufficiently forward biased and therefore not conduct at all.
You can observe such an effect for example with two LEDs, take a red LED and a blue LED, the red one will have forward drop much much lower than the blue one, if you put them both in parallel with a single resistor shared by both, the red one will light and the blue one won't because the blue one will no longer be sufficiently forward biased to pass current.