The company I work for does that as well for its retail environment, it sounds good on paper but the only thing it’s done is all the secondary phones now are ignored until it’s a transfer ring. After a certain time of day(when the receptionist goes home) it just won’t be answered unless a manager is the one who answers. This is partially due to the lack of training of the secondary and partially of the “no departments ever close” policy so if you answer it you are expected to help even if it’s on the opposite side in an area you know nothing about