Wasn't the idea behind bino marking so that people don't just leap onto the radio and literally call arty on enemy spawn 3 seconds into the match? Obviously you *can* call in arty quickly as long as LOS is available to mark the area. It certainly isn't perfect, nor realistic, but it does put a small limiter on (at least) early match abusing of arty on spawn points.
However, that is negated regardless if the map is designed poorly enough to allow LOS close/ontop of the other teams spawn at start. There needs to be atleast a short amount of time, even if its a mere 15/20 seconds to allow movement from each side.
Hence, thats how i view the role of binos in the use of arty.