I was trying out the Search Results web part and the Content Search web part, in order to decide which one is better for displaying sites. I noticed an interesting thing. When I put in the same query to return a list of sites, the Search Results returned only half of the sites. For example, I had /sites/p/n and /sites/p/n/ta, only latter was returned.
After reading a couple of articles, I realised the Search Results web part treats these 2 sites as duplicates. Therefore, only decided to display one for me. To make it to show all, just go to the Settings tab in the Build Your Query dialog box, select Don’t remove duplicates.