MacOS – Why does .tar.gz automatically extract the GZip archive when I download it in Safari

I downloaded a .tar.gz archive backup of a website. Every time I download it, when I click the magnifying glass in Safari Downloads, it takes me to the file, but it's now just a .tar, and so is double the size.

Nothing pops-up to say it's extracting.

Is it just Safari doing it?

I have "The Unarchiver", "Archive Utility", and "7GX" all installed ("Archive Utility" is the default). Or is it just the way macOS displays it, and it is still GZipped?

If I Zip it then it goes back to the size of the GZip. Safari also only says it downloads a file the size of the .tar.gz, not the .tar. Any ideas?

macOS Sierra 10.12.1 (16B2555) and Safari Version 10.0.1 (12602.2.14.0.7).