why the hotfix result is different by using Win32_QuickFixEngineering and UpdateSearchResult

Question

I want to get hotfix installed on my computer in C#, when I use wmi through Win32_QuickFixEngineering, I got 33 hotfix installed on my computer. But when I use WUApiLib through IUpdateSearcher, I got 19 hotfix installed on my computer. And I found that there are 2 hotfix which are in the 19 but not in the 33.

Method 1: wmi

ManagementObjectSearcher hotfixmos = new ManagementObjectSearcher("Select * from Win32_QuickFixEngineering");

Method 2: WUApi

UpdateSession UpdateSession = new UpdateSession();
IUpdateSearcher UpdateSearchResult = UpdateSession.CreateUpdateSearcher();
UpdateSearchResult.Online = false;
ISearchResult SearchResults = UpdateSearchResult.Search("IsInstalled=1");

Why they are different?