Fix Robots.txt and Sitemap.xml Creation Path in Magento 2

I have created a robots.txt and sitemap.xml files using Magento UI but when trying to access www.mydomain.com/robots.txt or www.mydomain.com/sitemap.xml it gives me 404 not found.

I found that robots.txt and sitemap.xml file are created in mydomain/http/, however, the pub directory is set to be my root so moving the file to the pub fixes the issue.

Why Magento created the files in this location?
If I want to make changes to the robots.txt file, I can't use the native Magento feature?
What is the best solution to this?

I am using NginX and added this to my configuration file which "solves" the issue, however I am not sure if this is the best solution:

# robots
location = /robots.txt {
    alias /var/www/example.com/html/robots.txt;
}

# sitemap
location = /sitemap.xml {
    alias /var/www/example.com/html/sitemap.xml;
}

I am using Magento 2.1.8.