Are the image data augmentation generators in Keras randomly applied
I suggest having a look at the relevant documentation.
There, it states:

rotation_range: Int. Degree range for random rotations.
...
horizontal_flip: Boolean. Randomly flip inputs horizontally.

Saying each of the operations is applied randomly, I would say, means your images will be generated sometime with and sometimes without the augmentation steps, independently from one another.
If that doesn't convince you, here is the relevant snippet from the source code:
if self.horizontal_flip:
    if np.random.random() &lt; 0.5:
        x = flip_axis(x, img_col_axis)

The code for the rotation step is a little more involved, but contained within the same class that I liked above.