I checked these points and found they are far away from a street. In some special areas where our zip codes can't cover, then no matched result will be returned. We have a zip codes area lists where you can find it in your Geocoder full dataset known as "zipBBX.txt". I visualized those areas and some of your points:
I also checked some points on Bing Reverse API, looks like they also returns on a city level. OSM does good better, it will include a nearest road. Try nominatim.openstreetmap.org/reverse?format=xml&lat=30.5523878&lon=-87.9484604&zoom=18&addressdetails=1
Personally, I admit there are some enhancements possible on it like we can consider to return a city if none street matched, but that will be taken another days on it.
Hope it helps.