That's the original way of controlling the analog inputs. It just controls whether the Arduino sends the analog messages. Its there only for backwards compatibility. Use the non-old messages now.
What are the non-old messages? Maybe I should study the firmata documentation instead of just playing around with these patches, but looking at the arduino-test and arduino-help patches I can't see any way of enabling analog inputs (i.e. have the arduino send them) other than these "old" messages.
I guess it's in front of my eyes and I don't see it...
thanks m.