Please take a look at this guide (1) here. I think you probably overlooked that when you change Choices, the entire "Choice list" is saved in the update set.

In my screenshot I changed several choices, which were all saved in the same choice list. This is the difference between created and updated timestamps.

1: https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB0656146