MacOS has a weird solution to throttling. They put a fake process in the process list which looks like it consuming x% of the resources but really it is just blocking some usage to allow the CPU to cool.
I wished they would have a separate, properly named process for it. My old MB Pro (late 2015) was throtteling a lot and it took me very long to recognize, as it was just "kernel task" gobbling up cpu. Getting the machine cleaned out at a service center did help a lot, I wonder, whether redoing the thermal paste on the cpu would have improved it further, but I ended up replacing it with a current model.
I love this tbh. It's a great indicator and allows me to easily use existing tracking/functions in Activity Monitor to assay thermal headroom at particular points etc