That is the way I read that statement. If you do not have a current custody order then you can file for custody with the courts. You would not have to show changed circumstances as you would with modifying an existing order. Though an agreement would hold up in court, this would be the initial custody suit as far as the courts are concerned.
This is why though it’s easier to have a signed agreement on custody during the separation, custody can still be filed for at any point.
As a side note: There are a lot more judges ruling in favor of equal time if the parents live close enough to each other and are able to work together for the child’s best interest.
My husband and his ex share joint custody with equal time and previously did two days here 3 day there and back and forth one day int he middle. They now have the arrangement that every Wed. the boys stay with their mother and every Thurs they stay with us. The rest of the week is with one parent and the next week with the other. This way, one day of every week they have to switch but that is it. I would prefer that it be the complete week but their mother’s work schedule prevents her from being able to do that and still have time with them.