The latest lang/siod port has an i386-only option: SQL_ORACLE. It also sets OPTIONS_SUB to have all of the options added to PLIST_SUB, as documented.
Unfortunately, the SQL_ORACLE="@comment " is NOT added to PLIST_SUB on non-i386 platforms -- and the port has to do it itself as a work-around.
The work-around should not be necessary...
To reproduce the problem, comment out the PLIST_SUB-amending line in the port's makefile and try "make clean check-plist" on any architecture except i386.