I would guess Sony would not do so for marketing reasons. Leica is known for offering relatively low-volume variants of their cameras, and with the prices they charge, can apparently afford to do so. Sony, on the other hand, seems to go for the models that can sell in volume.
Leica buyers, for the most part, have been esoteric purist types that would appreciate the small image quality gains that come from converting the Bayer quadrants on the sensor to finer gradation B&W pixels... and are willing to pay something north of 10,000 USD for body and lens to do so. I shot Leica film cameras for about 30 years, but I am more careful about how I now spend my money, today, now that I am retired
Would I purchase a Sony B&W model? Likely not, since I shoot on high resolution sensors and have good Photoshop skills. When I want to shoot B&W, I set one of my cards to B&W JPG's and the other to RAW (I erase the JPG's and process the RAW's into B&W). I can visualize my shots since I see B&W images in the viewfinder. The tiny bit of fine gradation I give-up by shooting a color Bayer, is offset by the flexibility to also shoot color in certain situations without carrying two cameras.