Okay, that's related to the machine you're connecting from.
In digging I found something else in TinyCore. The configuration file for sshd comes with X11 forwarding turned off. I had a vague memory of previously hand editing that file. This time I used nano to edit the configuration file.
$ sudo nano /usr/local/etc/ssh/sshd_config
In the file, next search for the text "X11Forwarding" and change that line and the next to look like the following:
X11Forwarding yes
X11DisplayOffset 10
With the edits made, to make it permanent you can insert the configuration file name to the end of /opt/.filetool.lst
but of course without the leading / . Next, reboot or otherwise restart/reload sshd
So far, so good.
Krista