I found the following lodged in the left fan of the laptop:

The platic tube is removed during assembly. The tube is a protector for the antennas used by the wifi card. They are supposed to be discarded. Somehow, in my case, the tube was discarded into the openings of the left fan(CPU heatsink fan). After removing it, the CPU does not throttle anymore.
When the issue was occuring, I noticed that the CPU was 100% throttled in Intel XTU. I noticed a very faint click sound as the fan was trying to spin, which eventually stopped since it fully jammed by the plastic tube. Finally, there was no air being pushed through the left fan slot when issue was occurring.
As for the other fan, *sigh*, the yellow wire used to control/power it was slightly curved towards the inner fan blades. It was about 2mm away from hitting the fan. This wire was taped in place and not properly cleared from the fan blades.
In summary, if you have throttling issues with CPU, check that the fan is even spinning. This may also be the issue for GPU throttling.