I didn’t think folks would actually type this. 
I, myself, can never remember how to spell Majjhima Nikaya, so I always type “MN”.
And if people really do wish to type Majjhima Nikaya, would they not simply omit the “1-50”?
Voice.suttacentral.net is designed for the visually impaired rather than the sighted. The Digital Pali Reader UI is optimized for the sighted and requires a lot of visual scanning to glean information. That information is indeed valuable at informing the reader about the overall structure of the Nikayas.
One of the challenges we have yet to solve is how to present the Nikayas to the visually impaired for those who wished to learn the Nikaya structure. Voice today has a search-engine UI where users type in a phrase of interest. This simple UI works very well for the visually impaired and is also of benefit to the sighted. Yet as you point out in your picture, we have failed at presenting the Nikaya structure to our users and will need to work out how to present the Nikaya structure to the visually impaired as a navigational and instructional aid.
Thank you for your picture–it presents a challenge we have not yet tackled.