You did not even bother to try it, did you?
Anyway: I would like to point out that this default value ALWAYS applies if you select more than just one file. And this value also gets written if you save the (other) modification.
Which means, that you may have just used the track numbering assistant to get a sequence but when you now save another modification, you get the default value back into the field.
To get around this I wonder if an action group that prepares files and that also sets the track number would be an alternative. Like that you get the dummy value only when you first treat the files but afterwards the data is not modified unintentionally.
But to find out which way is best is up to you.