ESD protection using capacitor
Yes, it probably does. An ESD pulse has very high voltage, still very low charge. If your finger+body would be represented as capacitor, it would be about 100pF, charged to (for example) 8kV.

\$ Q_{body} = C_{body}*V_{body} = 100pF * 8kV = 800nC \$  

When discharging to a 100nF capacitor the voltage becomes:  

\$ V = Q_{body} / (C_{body} + 100nF) = 800nC / 100.1 nF = 8V\$ 

I still would recommend also adding a resistor, it functions as RC filter as well then.

PS. the human body capacitance (HBC) is traditionally chosen as 100 pF