It seems Jira cloud API allows to update an option for a select list issue field via PUT /rest/api/3/field/{fieldKey}/option/{optionId} and if the option does not exist, a new option is created.
However, it is not allowed for Jira server. Also, if we import a csv in Jira server and map a column to select list field, a new option is created, if the option does not exist.
Why is this behaviour not consistent?