When trying to su admin from a root shell, I get "Real UID cannot exec script".
I'm no expert by any means with this stuff.....but it occurs to me the admin account for SME is an alias of root.
What leads me to this conclusion is when you log on using the shell under admin it should present you with the "SME Console" which is the shell partner to server-manager. Login to server-manger is done by admin username but has root permission. Mail for root is received by admin...etc.
The templating system gives them different jobs but root and admin seem to be fairly inter-related.
It's also my understanding if your logged on at a console or through a terminal session as "root" the "su" function is unnecessary.
Since no other information was given - such as SME version, method of logging in (say putty or consolel) or code being executed it may be a little hard to simply say there is a bug.
Like I said.....I ain't no expert - simply sharing an observation.