Bad implementation from the beginning.
When we edit a category - all its parent and children categories get a new SEO URL.
If I want to make a category SEO URL without its parent categories, I can do it via Design > SEO URL. But as soon as I edit a category - all SEO URLs including parents will be rewritten and parents will be added back to the category SEO URL.

@opencartbot
At least my solution fixes the destructive behavior.
I understand that categories usually are not edited very often. But in my situation the content manager changed one line in the first level category description and saved it. As a result we got over 200 destroyed category seo_urls. And of course this was noticed much later, when we started getting 404 errors in Google Search console.

Yes, I just noticed this issue today and your PR solves it.
Thanks!

@opencartbot At least my solution fixes the destructive behavior. I understand that categories usually are not edited very often. But in my situation the content manager changed one line in the first level category description and saved it. As a result we got over 200 destroyed category seo_urls. And of course this was noticed much later, when we started getting 404 errors in Google Search console.

I have created a pull-request for this which just uses the editCategory logic taken from OC 4.0.2.3 where this issue didn't exist, see #14501