Hi Mike,
Feel free to add features. I tried in a new web map without luck.
I may try recreating the service from scratch. I'm not sure what
the minimum requirements are for getting that value to default. 
IE do I need to specify the default in the Feature Class, MXD Feature Template
and in the AGOL Feature type template or just one or 2 of these. 
I'll experiment.
Regards,
Richard