That's much harder to do though, they need to continuously monitor new nodes and make sure blocking the IP does not have too much side effects unless I misunderstand how it works.
Blocking them is generally low impact but there is one exception: I believe Cloudflare’s gateway (cloudflare-ipfs.com) uses their regular CDN IP ranges so it’s the same level of difficulty as blocking any content on their service.
To be clear, IPFS is a neat idea. I would just be very hesitant to recommend its use to anyone who has to worry about government restrictions.