You guys did see the alone.
It was impossible to send spy units to Battleground alone if you intended them to defend, and not reinforce. But spy units where given category defense, instead of intelligence and now you can send them on defensive missions ALONE.
These kinds of fixes are categorized into bug. and are never announced. Like when they fix unit description saying its offensive when its really defensive.
To send spies to BG before you needed to send them with one defensive/offensive units. I build my bank mostly on spies and send 100 plus 1 archer every 48 hrs. I know what I am talking about.
Why would I spend 2 years sending 1 archer to BG when it was no really required. Then again I could have been wrong in my assumption that spies needed to be send with 1 units all these years, and was surprised after 2 years of playing that they can't.