If a competing photo storage site doesn't offer the same "feature" of scanning the files you upload, might Apple decide to prevent iOS devices from accessing it? I'm sure Apple would love to claim that the anti-trust authorities don't care about the children.
There's no precedence for any browser to censor any website outside of malicious website feature. So technically you're right, Apple surely could do that, but that will be another level of fence around garden.
If a competing photo storage site doesn't offer the same "feature" of scanning the files you upload, might Apple decide to prevent iOS devices from accessing it? I'm sure Apple would love to claim that the anti-trust authorities don't care about the children.