David,
I believe that the group decision was
obviously ambiguous. In discussing elements,
optional would, to me, be understood to mean
something about possible zero cardinality.
Your interpretation is apparently not
universally accepted. So what you think
people agreed to is not what they thought
they agreed to.
Sounds like this is something needing
a fix, one way or the other. To say
that it is a functionality change implies that it
had been unambigous what was agreed to.
But it was not unambiguous. Therefore,
it is not a change in functionality.
Dale Moberg