This argument isn't obvious to me, and I don't find the docstrings clear enough to understand what's going on. I think the English grammar isn't quite correct (happy to help there if necessary). I would appreciate further explanation here:

https://github.com/Project-MONAI/MONAI/blob/dev/monai/networks/nets/flexible_unet.py#L243-L244