It is not, whether one is harder or easier than the other, the top of the top at both systems are impressive and hard to obtain in their own right. The reason the “Console top 500 = gold PC” what ever statement was made, is cause FPS games are made for M/KB, they are way more suited for it and is indeed the superior system for it, just like platformers were made for joysticks omnidirectional movement.
Consoles need aim assists in its base form to even function right and play good for the vast majority of players, that is a huge flaw in and of itself.
If you ever were to pit a top 500 fps player vs a top 500 fps console player, the difference in precision, flick timings and reaction times should be evident, even so beyond the limitations of the systems.
Even so, we have seen very few cases of people going from a high rank on console to a higher rank on PC. The Genji one trick “Arikadou” i think and the Lucio one trick.
Both of these heroes are in no way severely capped by their aiming capabilities, so the most notories things to learn, gameplay, maps, game knowledge etc, was already there from console and transfer right over to pc. All they needed was to get familiar with and comfortable with the aiming style. Even so they needed some +200 competetive games and around a + 100 levels of PC gaming to begin rising to higher ranks on PC, which is quite a bit.
As another reference of how this works. I have reached top 500 multiple times before, i have played at high scrim levels. I have a 15 year background in CS and other FPS games and so on. My friend, who to this day still plays and scrims at a higher level than i did, is 4.4-4.6k rated consistently throughout many seasons, have no chance at beating me on Widow, Mccree, Ashe, Soldier. Even though i have put no hours into the game, the last couple of months i would shred his a** (And have done so before) in a 1v1 scenario, where raw aiming means a lot. This is cause his first FPS was Overwatch, while mine was CS, way back, i have far more experience and practice using the mouse, so i my skills transfers over to other games, rather instinctively.