Why SMPS call for multiple input capacitors
As far as I can tell a single aluminum polymer cap is better and cheaper than the 4 tantalums specified by the datasheet. ESL for the aluminum polymer I cited is zero at the 260K frequency this SMPS operates at.

Ripple Current rating is 2.8A versus 4 x 0.63A = 2.52A

Voltage Rating is 10V lower, but doesn't require as much derating as the tantalum, and I'm using overvoltage protection at 18V anyway for my application.

At 47uF it's a little higher capacitance than the 4x10uF specified in the datasheet

As far I can tell there's no reason to prefer the capacitors the datasheet is calling for. I did notice the datasheet was authored in 2004 and last revised in 2016, so hopefully it's just a matter of outdated docs not keeping with newer capacitor technology.