screencapture to file starting with dot

On Mac 10.13:

% /usr/sbin/screencapture ./.foo.png; echo $?

0

Mac 10.14:

% /usr/sbin/screencapture ./.foo.png; echo $?

screencapture: cannot write file to intended destination, ./.foo.png

0

Two issues on which I'm seeking clarification:

1. It appears you can't screencapture to a file starting with a dot (".") prefix in Mojave. Is this intended behavior?
2. Given the failure to write the file, I would expect the exit-status code to be non-zero. Return zero causes later issues in my software's logic when the file doesn't exist.