Sometimes, the competitor keyword report might not show all keywords for which any website ranks. This is because one competitor keyword report is only for one single location. The missing keywords in the report might belong to a different location.
Here is an example. You might own a website which is popular in multiple countries and you run a competitor keyword report for the US location. You see that the report doesn’t show some of the keywords. You might find the same missing keywords when you run a report for some other location (say, the UK).