I cannot get Tftpd64 (v4.64, I also tried 4.62) to create a named pipe for syslog. Using the Sysinternals pipelist utility, or the powershell command at the bottom of the post, I cannot see a pipe named tftpd32syslog. Looking at this post from 2012, it seems the function may be broken.
[System.IO.Directory}::GetFiles("\\.\pipe\")