True enough.. any special reason for this? Is this intended or a bug?

I have a slider that I would like to send it's value. I'm using the $0 variable in the send name so I can have multiple instances of the patch running without conflicts. If I connect the slider to a "send a-$0" it works, but if I fill the "send symbol" field inside the slider's properties (because this way the patch can be cleaner), when I put a $0 in the name it, next time I open the properties the $ is gone. i.e. I put "a-$0" there and if I close and open the properties again I have "a-0".
Is there a way to use variables inside the properties?
Adding some info, it seems to work with Number objects, but not with Slider and Radio... probably it's a bug, then.