Hoe big a percentage of FBI / DoJ employees are running linux (with imagemagick) as their work computer? I'd be surprised to see a similar oneliner for a stock windows installation.
Yeah they might have used some web converter, but that on the other hand would have been extremely incompetent handling of the secret data.
Installing MSYS2 is a matter of a few minutes. There is also WSL and macOS features a POSIX shell, imagemagick is likely already installed as a dependency somewhere, like ffmpeg often also is.