The startup script for pcmanfm is hardcoded with the user tc. It would be nice for it to read the username from /etc/sysconfig/tcuser.
I see your point, however it is not so trivial. Startup script is executed before saved data restored ant it may overwrite /etc/sysconfig/tcuser
Also if there is a different user specified it is required to check /etc/passwd to check user exists, its home directory setting, etc. I would postpone it for a later time.
What is more trivial to add it to /root
To be honest it is not a pcmanfm business, more it is up to the gtk+ environment. It is done by pcmanfm and wicd only to fix its lack and to make them working
as a victim. Possibly other applications are missing it also.