Seems to be fixed for 18w46a, tried with two accounts and 20k block apart, crop growth and leaf decay works. Will check with multiple players.
EDIT: confirmed with multiple players, server is ticking properly and mobs are spawning. Server is overloaded however even with few players.
Can confirm for 18w45a. Crop growth, mob spawns, leaf decay only if alone or everyone in one chunk.
Confirmed for 1.9
Joona Jokivuori
Seems to be fixed for 18w46a, tried with two accounts and 20k block apart, crop growth and leaf decay works. Will check with multiple players.
EDIT: confirmed with multiple players, server is ticking properly and mobs are spawning. Server is overloaded however even with few players.