if i wanted to make a connected glass texture pack where all stained glass variants to connect to each other as if they were the same block, thats just entirely impossible. there is many blocks in the game that are very similar to the point of being almost the same, but are classified as different blocks. being able to specify other blocks to also connect to would allow for texture pack creators to have more freedom in connected textures

This is planned for the next update or update after that.