You're right - a URL is either a technically valid URL or it isn't, but in this context, we're clearly talking about links to phishing sites (or not).
As someone who operates a service that allows people to create and share lists of links on a public site, I can tell you from experience that it's not as innocuous as you might think. Scammers routinely use a trusted domain to host a link to their malicious final destination since the initial, trusted domain in often the one given the most scrutiny (e.g., from an email). It sounds silly to more technical users who understand how the web works, but unfortunately it's effective and super popular in phishing campaigns.
To your point, yes - a list of phishing URLs would be useful in a lot of cases, but it's difficult for automated tools to tell the difference between those legitimate use cases and the much more common cases used for phishing, so they err on the side of caution. As mentioned, the human review / appeal process surely has room for improvement.
What is wrong with a list of phishing urls ?
Sounds simultaneously useful and innocuous to me …