> There is a big causal step between "phones slightly warm brains" and "that causes headaches".
> Fortunately we don't need to rely on the fact that it would be “hardly surprising” because there is good quality empirical evidence disproving the relationship.
I wish people/you would either be more open minded or at least do a quick Google search. Literally searching for "brain heating headache" got these results which suggest that there is evidence showing a possible relationship. I am not even sure if this conversation is in good faith anymore.
https://www.healthline.com/health/heat-headache
https://pubmed.ncbi.nlm.nih.gov/24581675/