ModelCheckpoint docs for every_n_epochs==None

The docs for ModelCheckpoint say:

every_n_epochs: Number of epochs between checkpoints.
If every_n_epochs == None or every_n_epochs == 0, we skip saving when the epoch ends.
To disable, set every_n_epochs = 0. This value must be None or non-negative.

However, by default every_n_epochs==None, and in the simplest case of

checkpoint_callback = ModelCheckpoint(monitor="val_loss")
trainer = Trainer(callbacks=[checkpoint_callback])

it seems like checkpoints are still saved. Are the docs correct?