Even in ARR that was only a thing for the first 20 (?) - for the second batch you had to unlock all vistas aswell.

The paintings can be sold/bought on the marketboard aswell - or be bought by a friend/someone who has it unlocked. Its a nice way to have some income for those people who can do jump puzzles but dont care about crafting. I didnt bother with the sightseeing log since ARR, so I had a friend buy me the new stuff.
Case and point: paintings can be traded, you can get them even without unlocking them.