Current carrying capabilities of surface mount ICs
Assume the pins conduct about as well as AWG 28.  That's a resistance of 0.106 ohms per meter.

The pins of an SOIC8 are approximately 2mm long.

You split the current between two pins, so you halve the resistance.

That'd be something like \$ \frac{0.002m \times 0.213 ohms/m}{2}= 0.000213 ohms\$

At 50A, that's a voltage drop of 0.01065V.  

Total power dissipated in one pair of pins is then about 0.53 watts.

The 50A sounds scary, but the total power lost through the pins is fairly small.  You still need to get rid of the heat, though.

That's why datasheet shows that the evaluation board has those great honking copper areas attached to those pins:





The values above aren't necessarily exact.  They are intended to show that even though the current seems outrageously high, the total loss as heat will be much lower than a first glance suggests.