elem/2 is guard safe, I think thats the main reason why it is in Kernel.
put_elem is probably in Kernel to line up with put_in/2/3, but I’d like to not see it there as it involves the cost of copying the full tuple.
Tuple.append/2 is probably in its very own module, because it involves the cost of copying should be carefully thought upon before just using it.
These are assumptions based on observations mixed with a bit of personal opinion.
