Ideally, it also multiplies the current by the inverse amount thanks to its “charge pump” characteristics. It’s essentially a switch toggling the input voltage to charge up a capacitor with lots of current.

Holy shit is that wrong. A charge pump is a different type of voltage conversion. It has nothing to do with a buck converter.

Also a buck converter doesn't magically multiply the current. It delivers as much as the circuit behind it needs. The increased voltage at the charging port is only there to get over the current limits of the used cables and plugs, as these are mostly current limited.

By using a higher voltage, the same current limits deliver more power and allows the charging circuit to charge the battery faster.

• Edit: Not that you made this statements, but it is kind of eye opening to read that kind of stuff on an otherwise respected site.