This is true. Extensions currently (manifest v2) are able to evaluate net requests dynamically, and are able to modify requests according to a dynamic ruleset that the extension can retrieve from some filter list published on the internet.

Under manifest v3, extensions are not able to dynamically inspect requests, instead, they may only apply rules to net requests. Even worse, there is a limitation of only 5000 rules per extension!! [1]

Even WORSE worse, under Chrome's manifest v3 rules, the extension cannot load any external code! Meaning that blocklists must be packaged with the extension. [2] Now, one might consider the reading of that link to no affect block lists, it's not a "library" and it's not "code" so long as it's just a list of textual rules.... however, google considers the following to be a violation: "Building an interpreter to run complex commands fetched from a remote source, even if those commands are fetched as data". [3]

Sneaky sneaky. An extension update (and hence new app store submission) is required to update filter lists.

In other words, dynamic net requests are banned, and remotely-updated blocklists are banned as well.

[1] https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...

[2] https://developer.chrome.com/docs/extensions/develop/migrate...

[3] https://developer.chrome.com/docs/webstore/program-policies/...