The datasheet waveform suggests similar clamping voltages as for the first diode. The question is, what does it matter for your design if you had a clamping voltage spec of 16 versus 10V @10 A? Both values are far beyond maximum ratings of the protected chip.
External ESD protection works in combination with internal protection circuit, extending ESD rating from 1 or 2 kV to e.g. 8 or 16 kV. Protection has to be verified in the final layout, it depends on many parameters like parasitic inductance.