Now that's being technical. For all design purposes, it's still a separate button with symmetry to the Square button across the Y-axis. Yet that's beside the point.Square button. It doesn't 'click'. And, the right directional button isn't a button, it's a componant of a dpad, which isn't really a button. It's kinda a switch which depending on the direction pressed determins which of x directions are mapped to. a d-pad is one unit rather than four buttons.
If the square button doesn't click when pressed, then the PSP has a broken button, and isn't related to the design of it. Unless you mean "click" design wise, in which case it can still be gotten used to.