Great move by LATAM, creating more confusion and problems where they don't need to exist. I can only guess that it was their intent to make customers frustrated, and give up on the idea of redeeming km/miles/points altogether.
If management were serious about making the customer experience better, they would have left things alone. ONE website to book and redeem flights, whether paying for a ticket with cash or miles/points. (As many issues as AA and UA may have, even they keep it simple in this regard.) Even after reading LATAM's silly email and link about Multiplus, I fail to see them listing any actual benefits of this new system.