See Page 230.200 Exhibit 230.31. Thats the way it is. the disconnects are remote from the transformers line sideas per 230.204 (B)location per 230.205(A) which refers you to 230.70 (A)
Load side of transformers Disconnect switchs in Building Nearest point of entrance 240.21 (C) 4.
Customer owned transfromers need overcurrent protection per article 450.
Single phase cutouts cannot be used as the service disconnect device. Although they can be used to provide overcurrent protection for the service, feeder conductors, or transformers.
As George keeps saying, above 600V the service disconnect must be a multi-pole device. Also,location is not as important as is the type of equipment.