I see, I"m positive that it was possible before since I ventured off on a raft just 2 days ago just fine. I had never crafted a boat but rather a raft to get off starter Yland and then jump straight to Ship.
Good to know it's at least intentional and not a bug, albeit the Codex might be updated with the fact that rafts cannot be claimed or used for ocean travel - it makes sense logic wise ofc unless you're in a very desperate situation, but it is something that used to be possible in the last version.
I had assumed that boats require Planks to build (which require a saw, which requires metal that is not available on the starter Yland)
Looking forward to try the rest of the update this weekend then!