In Javascript, should appending to the signature of a callback be considered a breaking change?

I.e. given an operation op(target, callback) should changing it from callback(item, index, array) to callback(item, index, array, root) result in a new major release according to semver?

The spec specifies:

increment the MAJOR version when you make incompatible API changes

and the two signatures are not incompatible, as the new one encompasses the old, seeming to suggest a new major version is not required.

On the other hand, consider this (admittedly slightly contrived) example:

function doTheThing(item, index, array, doItDifferently) {
    if (doItDifferently) 
        // Do something unusual and amazing with the arguments
    else
        // Do the same old boring thing with the arguments
}
// Use doTheThing as a callback to the operation:
op(target, doTheThing)
// doTheThing is also used directly:
doTheThing(arr[0],0,arr,true)

doTheThing is a valid callback, but might be used elsewhere in the code in its more elaborate form. This would break if the callback signature were changed.