Of course it can, one doesn't need to test this. It's not as if any browser would allocate and burn the cpu at 100% for 30 seconds and then stop all javascript

Of course it can, one doesn't need to test this. It's not as if any browser would allocate and burn the cpu at 100% for 30 seconds and then stop all javascript execution or css rendering or anything on the page. That's the kind of solutions you're looking at to fix this. This is like research to confirm the sky is blue. Good to know for sure but we're rather sure to begin with. If you want to try it, a power meter is a good thing to have anyhow, or someone could lend you one. Plug it in and load different websites a few times, then look how many joules you used. Not every site can be told apart with a limited measurement like this, especially on the lighter end of the spectrum, but if you want to know if Tor Browser mitigates this then you can confirm it this way.