Short answer: You are probably confusing the sensor bit depth with the output file bit depth.
There are two completely different and mostly unrelated bit depths:
There is the bit per pixel of the sensor and the raw file (in your case 14 bits) this does not relate the the color space in any way because those values are before the demosaicing algorthem turns the values into colors.
Then there's the bit per color of the result image - this is what you select in Lightroom's (or any other raw processor) export module - this should be 16 bits for wide gamut color spaces (doesn't have to be but it can help).
Those are mostly unrelated, you can have a 32bit output from a 14bit raw file (this does not waste bits, it gives you more accurate processing if you edit the image file and apply more processing in the future) and you can create a 8bit image from a 32bit source (done all the time in HDR rpocessing)
What to do: unless you have a specific reason to do otherwise use sRGB
All consumer screens and printers use sRGB so using a wider gamut system only introduces an automatic translation between the image and the viewer who will do a worse job than if you process the image in sRGB to begin with.
The number of bits is not directly related to the color space.
The number of bits tells you how many steps there are between (for example) (0% red, 0% green, 0% blue) and (100% red, 0% green, 0% blue).
The color space, on the other hand tells you what real world color is (100% red, 0% green, 0% blue) that we talked about.
The raw file does not have a color space, there isn't an sRGB raw and a ProPhoto raw, the "color space" of the raw file is fixed and depends on the properties of the little physical color filters that are in front of each pixel.
When you process the raw file into an image you can choose what color space to work in and what will be the color space of the result image.
not having enough bits to represent a smooth transition can cause bending and having a wider gamut color space can make the situation worse by making the real color of the "steps" more different - but this is in the output image file not in the raw sensor data.
So, if you must use ProPhoto or AdobeRGB save your processed image as a 16bit TIFF and not a JPEG, PNG, 8bit TIFF - that seems like good advice and doesn't have any relation to the number of bits produced by your camera's sensor.
But since virtually no one in the world except photp/graphic experts uses 16bit TIFFs you will have to convert it to a 8bit JPEG (probably in sRGB) before anyone can view/use the image.