I'm glad to see someone using the SOSLIB and taking the trouble to suggest improvements!
Indeed,
%u returns the Windows/ATE username (if applicable). After reviewing the code and your suggestion, I decided to just go ahead and implement a new variable
%l (perhaps suggesting the mnemonic "login") which ignores the Windows/ATE login and returns the A-Shell application/server login. (I made a few other minor improvements and cleanups at the same time.)
I've posted the updated
fnsprintf.bsi to the
SOSLIB repository. (The first link will only be valid until the next update; but the second link should be reasonably permanent, from which point you can drill down to the 907010 directory and fnsprintf.bsi file.)