Haven’t looked at this closely, but it wouldn’t be the only unexpected observer notification I’ve encountered with JS live api. (I remember getting some callbacks with “id 0” arguments, perhaps when moving an device with some observed property or something like that, and then a second callback with the expected/valid id.)
I dont recall if I did side-by-side comparison with max api objects to see if the notifications are different. Certainly would expect them to be the same. Did you?