Why is CPU not used at all during replays?

1. Why is CPU not used at all during replays? It's so laggy in a scene with over 20 objects in the scene interacting. I don't understand... Is it because I initially recorded the replay in laggy conditions? For example, theoretically, if I recorded the replay in laggy conditions with an 8-core CPU, and exported the replay to a computer with 64-core CPU in it, if I play this replay on the latter computer, would the replay be just as laggy?
2. It's funny how even on pause the FPS is at ~50, but when you move the camera a few kilometers from the crash scene, the FPS goes back to limited but normal ~70, and the CPU is like at 12% usage on whether you're near the scene or far.
3. Laptop specs:

CPU: 11th Gen Intel(R) Core(TM) i9-11980HK
RAM: 64 GB DDR4
GPU: NVIDIA GeForce RTX 3080 Laptop GPU
SSD: 2 TB Intel Raid 0 Volume

 

I'm not sure how the replay system works exactly but if it only plays some recorded movement and doesn't have to simulate anything the cpu has no reason to be used.

 

If it doesn't have to 'simulate anything', why do I have 3 FPS in realtime while Task Manager doesn't show me any bottlenecks?

P.S. I'm talking about a replay that got recorded with time slowed down by 16.
CPU usage: 12% (55C)
GPU: 40% (60C)
RAM: 19.8/63.8 GB

SSD: 0%

 

The problem is probably gpu related then
Or maybe it does simulate the physics and then it's just the replay system that is broken, there is a reason they removed the tab from the pause menu

 

Which tab did they remove? Btw, I edited my previous post.

 

If you press ESC while in freeroam there used to be a replay tab, now it's gone