why do we need to change the map to update the mod to u49?

Because if Update 49 is on 1.13, it will mess up blocks and it will be a sheer and utter mess.

It wont be on 1.13 probably, im asking why they need to erase the map

It could be one of many things then.

A. It needs to be done.

B. Update 49 may conflict with blocks on the map.

C. None or all of the above.

To y knowledge there is nothing in update 49 which would require the map to be reset. Unless there is other reason for it. Have you seen somewhere which states that it is?

Will U 49 be announced formally like usual on the youtube channel when it comes? Also where does it say the map needs to be erased??????

Oh thank god