Simply invoke the update agent from GNOME or wherever, try to connect, it gives an error due to missing sparc64 directory. Running up2date by hand via "sparc32 up2date" makes it connect and retrieve package lists properly. But I am rather sure that it will then not handle the kernel/glibc/etc. sparc64 specific packages correctly when some updates arrive for them.
this will be obsoleted by the new MSP software, and I don't believe we will be fixing it for 6.1/6.2.