The only thing I can think of is that it can't be fixed with the current state of technology and the way how their engine works. The reason could be how the level and environment, including events, are dynamically loaded as you play the game. Part of this is due to the "AI director" that can dynamically change what happens next depending on your actions. The entire "streaming pipeline" can't process and catch up in time the higher the framerate. That's why it's less noticeable at lower fixed frame rates.
To fix this and make it more "scalable" they need to rework their entire engine. It could be a "physics are bound to framerate and tuned to 60hz" - type of scenario. Maybe this problem could be mitigated if they utilized "direct storage" on PC in the first place.
If you want to see how “seamless and instant level/asset streaming” is done right, check out Ratchet & Clank: Rift Apart on PS5.