The difference between restoring STDOUT and re-opening it to /dev/tty is the case where STDOUT wasn't originally connected to the user's terminal.

For example, if the output was redirected to a file by the user starting the program, if STDOUT were restored any output after it was restored would go to the file; if it were re-opened to /dev/tty output would start out going to the file, but after STDOUT was re-opened further output would go to the terminal.

It's not completely clear from the OPs question which behavior is desired, so it's quite possible opening /dev/tty is the right solution.