GNU coreutils accepts special files like /dev/stdin without any issues, for e.g.:

$ echo 'foo' | install /dev/stdin test

That creates a file called test with foo\n as its contents, which isn't surprising.

However our coreutils fail with the same usage with this error:

install: cannot install '/dev/stdin' to 'test': Invalid input parameter

This issue doesn't effect cp, however it might effect other utils which haven't been tested.