Same FPS, slower games?

[CacoFFF]

I'll explain better:

This is a quick way of showing how a game works, you have the main world, the entities (weapons, enemies, you, etc), the rendering system.
A game follow this logic:

Main World >
Update All entities physics and other stuff >
Send packets for netplay >
Tell the render system to make a snapshot of the player's current point of view > (different games handle this in many different ways like: Pre Render, Render Overlays, Post Render for old Unreal Engine)

That whole process is usually done 60 times a second, greater if you disabled the 60 fps limit, lesser if your pc isn't strong enough.
Say, (1/60)s is 0.017s.
The game follows the logic, updates everything and checks how much time it took:
If the time is < 0.017s (fast pc), on a 60fps limited game, it will wait until time equals 0.017s to update again, otherwise it will go on updating as fast as it can.
If the time is > 0.017s (slow pc), the next update will be updated with a different Time value (the one that it actually took, the one > 0.017s, let's call it DELTA)

In a game, a projectile moves with a speed of 100 m/s, when that projectile is 'updated' will be placed away in the direction it is going by a 100m * DELTA. On a fast pc, DELTA is tiny, on a slow pc, DELTA is huge, but in the end, we'll see the projectile moving the same speed on both computer regardless their FPS. (Yes, objects don't 'move', they are relocated every frame in games)