The information comes from the same source that supplies the Maps application -- Google. If you don't like the answers, the only recourse you have at the moment is to ask different questions. Usually "-name" added to the end of the search string will remove "name" from the matches, but sometimes it also has unwanted effects on the results. My grocery store context search string has the names of all of the chains and individual stores where I'm willing to shop, joined by "OR" between the names, and with a couple of big chains tossed in at the end to make it more likely that it will tell me about some grocery store if I'm far from my usual haunts. I may not discover the fabulous yuppie supermarket just around the corner from my hotel unless I cross-check with the Maps app, but so it goes -- I'm most interested in making the usual case work well for me.
There have been requests to have the nearby feature return multiple choices instead of just the nearest hit. Use Send Feedback or email
omnifocus-iphone@omnigroup.com to add your vote if you think that change would help you.