Hi,
No matter if 16v or 25v.
Capacitors C8 and C11 are used to filter respectively, the 5 volts line and the unregulated 5 volts line.
The manual say, C8 : 470 µF 16 v and C11 : 470 µF 35 v
But they really planned oversized ! You can mount almost any voltage, even 10 volts models would be sufficient.
On the first board, they used a 25 volts for C8, because they probably no longer had 16 volts on hand.
In fact, one does not have too much to worry about the voltage, but rather the size of the capacitor so that it fits on the board.
As they found a 25 volts model small enough, they used it.
Usually, the higher the voltage, the larger the size of the chemical capacitor.
But technology is evolving, and there are now 25-volts models, same or smaller than the 16-volts models of a few years ago.