This has come up several times on the forum.
When you shoot in RAW mode, most in-camera settings such as B&W, sharpening, picture styles etc. are not actually applied to the image. Instead, the camera manufacturer includes instructions in the file on how it should be converted. So far, so good.
Unfortunately these instructions are often stored in the manufacturer's notes rather than in an open form and are only read by the manufacturer's own software. So only Canon software will read the B&W setting from a Canon camera, only Nikon software will read the B&W settings from a Nikon camera etc.
Ian