The other day, I applied for vietnamese visa online, and they sent me an approval letter with a list of about 18 traveler names, their birth dates, passport numbers, and nationalities including mine. In the email it says it's a normal practice for them. I definitely didn't know about this when applying and am not happy.
It's just the way the visa on arrival process works. Not great but I don't think there's a way around it for VOA. I had the same thing happen to myself a few years ago and was a bit surprised myself.
Where did you apply for your visa? I'm going to be applying for my Vietnam Visa soon and was thinking of using the E-VISA but I know there are a lot of private companies that somehow get you a Visa.