MacBook Pro slows down from pressure on the bottom (messy solution included)
I would re-seat all the temperature sensor connectors.

I've read that when the machine appears hot, kernel_task slows the machine down in order to reduce the heat.  The way it does this causes the CPU usage of kernel_task to appear high.

So perhaps, when you press on the cover, this distorts one of the temperature sensor cables, causing some faulty temperature readings.  (I'm assuming the machine doesn't seem hot to you?)

I did a search for [kernel_task CPU heat] and found this blog post, which describes a way to "fix" this issue by modifying the kernel_task configuration so it doesn't take this action.  I'd caution against this modification, though, as it doesn't fix the underlying hardware problem -- instead, it disables a (presumably important) software-based safety mechanism.