press release said 10 which implies only 10 were ordered. if 66
were ordered, it would have been explicitly mentioned right?
That's what I think too. The 66 must be some untrue rumors then.

If they ordered 66 of them, SMRT would have said that they
would buy 66 and introduce them progressively from March onwards
with the first 10 coming. Just like what it was for the OC500LEs
last time. But they only officially said 10 buses.
But why only 9 of them came??? Maybe the demostrator is included
as well into the 10 buses, which means that the demostrator is
confirmed keep for service. 