Using GPIOs marked as "standard drive, low frequency" for SPI on nrf52840

I want to understand the meaning of "standard drive, low frequency" GPIO pins. The datasheet mentions to use these pins for frequencies below 10 KHz. Does this limitation apply if I use SPIM on these pins? I tried running the SPIM at 8MHz and did not see any problem. Is it recommended to use only high frequency pins for SPIM?