While a block is powerful, it is not 100% airtight in every scenario:

LinkedIn’s blocking behavior described above applied in 2021 and is consistent with LinkedIn’s documented blocking features: mutual invisibility, removal of connection/messages, no notification, and the public-content caveat.

Your profile will not appear in their search results, and if they try to access your URL directly, they will likely see an "unavailable" message. Mutual Disconnection:

While a block is comprehensive within the platform, certain scenarios may still allow some visibility: Block a member - overview | LinkedIn Help

As of 2021 (and still generally true today), when you block someone on LinkedIn: