The 'i.MX RT Series Crossover MCUs' 'Key Features' table found at:
says the RT1020 is at 600Mhz, but the document:
'i.MX RT1020 Processor Reference Manual, Rev. 1, 12/2018'
refers to a 500Mhz clock from the main PLL, although there are other PLLs, but none providing 600MHz that I can see.
Also if you click on the RT1020 link in the table, the blurb says "The i.MX RT1020 runs on the Arm® Cortex®-M7 core at 500 MHz."
So there you have it. Table is wrong.