if(EXISTS path) doesn't expand tilde to $HOME

On Linux (and I suspect other Unix-based systems) if(EXISTS ~/something-existing) always fails. It seems that the tilde is not expanded and the check is performed for the path ./\~/something-existing with a literal tilde in the path.

I noticed that the same happens for file(DOWNLOAD's target path and I suspect it happens for other functions (though not all. include seems to expand it).

Is this the expected behavior? If yes, then I think it should be documented. I couldn't find any docs about that.