1903 KB4505057 installed twice. Why?

Today, I used the iso file to install ver 1903.
When completed, I checked the winver and confirmed build 18362.116 was installed.
That was about 4 hours ago.
Just now I got notification to Restart. I went to Updates & Security and found out that KB4505057 had been installed again.
Why is that?

I can't offer a reason why, but I can tell you that I just looked at 4 different systems that all had the May updates already installed. Oddly enough, when I looked at the installation history, 3 of those 4 systems did not show KB4505057 as being installed although I could swear it was installed on those systems. When I checked for updates KB4505057 was then installed on all of those systems.

I'm just noticing that KB4505057 came out a week after patch Tuesday. So, in my case, it's possible that I really didn't have this update installed as yet. In fact, thinking back, I'm pretty sure that I was on 18362.113 rather than 116.

But in your case, I'm just wondering:

In your screenshot, I see that KB4495620 and KB4497932 were also being installed, yet those updates were released a week before KB4505057. They were released on Patch Tuesday along with what was the latest cumulative update at that time (KB4497936). KB4505057 came a week later. The fact that those older updates are also being installed makes me think it unlikely that KB4505057 was already installed.

I'm just wondering if the ISO you used was really up to date since several other older updates were also being installed. Was this an ISO image that you added the latest updates to? I have not seen any Microsoft released ISO's that included updates as recent as May 20th yet.

Ah, okay. That makes sense.

I don't know about this specific update, but I have seen multiple instances in the past of people complaining that Windows installed various updates more than once. I've never seen a satisfactory answer as to what the cause in any of those cases was.