I have a choice type with a choice which is labelled "0", when I display it, I have 1 (which is the position of the choice in the choiceList) instead of 0 in my label.

The problem comes from FieldType::55 :
$builder->setAttribute('label', $options['label'] ?: $this->humanize($builder->getName()));
should be
$builder->setAttribute('label', strlen($options['label']) ? $options['label'] : $this->humanize($builder->getName()))