16 bit depth image is converted to 8 bit depth by sips

I am using MacBook Pro M1 with macOS 15.2. When I run “sips -s format png input.tiff -o output.png -m AdobeRGB.icc”, the generated png image has 8 bit color depth instead of the original 16 bit depth. But when I run “sips -s format png input.tiff -o output.png”, the generated png image has 16 bit color depth.