[tetromino_]

In English this is called "elimination communication" or EC. The parent subconsciously figures out when the baby needs to go based on schedule, observation of milk/water intake, and subtle behavioral cues (facial expression change, posture, etc).

It's a system that works quite well if the baby is exclusively cared for by a stay-at-home parent or a long-term nanny (and no other babies or toddlers in the house to distract the parent/nanny). But try to leave the baby with a new sitter or at a daycare - they have no idea what your baby's cues are and cannot be bothered to learn them; so back in diapers the baby goes.

[knallfrosch]

We have 1 year of paid parental leave (although only ~60% of your salary) in Germany, so almost everyone can do it.

[n4r9]

What happens after a year when the parents go back to work? The baby goes to the potty by themselves at that point?