is PSEL register setting for resp. peripheral automatically configure IO pin setting ?

Question

#include "nrf_delay.h"
#include "nrf_gpio.h"

void uart_init()
{
 
 NRF_UART0->BAUDRATE = 0x01D7E000;
 NRF_UART0->CONFIG = 0x00000001;

 NRF_UART0->PSELRTS = 5;
 NRF_UART0->PSELTXD = 6;
 NRF_UART0->PSELCTS = 7;
 NRF_UART0->PSELRXD = 8;
 
// nrf_gpio_cfg_output(6);
// nrf_gpio_cfg_input(8, GPIO_PIN_CNF_PULL_Disabled);
// 
// nrf_gpio_cfg_output(5);
// nrf_gpio_cfg_input(7, GPIO_PIN_CNF_PULL_Disabled);

 NRF_UART0->ENABLE = 0x00000004;
 
 NRF_UART0->TASKS_STARTTX = 1;

}

void uart_write(unsigned char data)
{
 NRF_UART0->TXD = data;
 
 while(NRF_UART0->EVENTS_TXDRDY==0){}

 NRF_UART0->EVENTS_TXDRDY = 0; 

}

int main(void)
{
 NRF_P0->DIR |= 0x000E0000;
 NRF_P0->OUTSET |= 0x000E0000;
 
 uart_init();

 while(1) 
 {
 
 NRF_P0->OUT^=0x00080000;
 
 uart_write('@');
 
 nrf_delay_ms(100);

 }
}
 
 This is working code for uart transmitter using direct register access.
My question : is PSEL register setting for resp. peripheral automatically configure IO pin setting ? 
 As per my board pins. 5,6,7,8 are connected to RTS, TXD, CTS, RXD resp. to CP2101.
So is it necessary to configure pins 5,6,7,8 for input, output, pull-up, pull-down OR PSEL setting automatically takes care of it ?? 
 Because even after I comment out IO setting , there is no effect on working. 
 Excuse me for my English !!