One of the biggest challenges with mapping house numbers is simply getting to that street to begin with. It takes a volunteer making an effort to go to various parts of town that he/she doedn't normally go to, since most neighbourhoods don't have their own local mappers interested in adding house numbers.

Once someone has made that effort, then it isn't too much extra effort to do all the house numbers. So, no need to restrict oneself to the middle of the range.

OSMAnd's address search feature already allows you to choose from among the house numbers that do exist for a street, even if the whole street isn't mapped, so it is often easy to navigate to the general ballpark of your destination.