Precisely, and this is why I've never trusted online "free" converters since day one. Who the fuck knows what they're actually doing with your file, and I always assumed that most of them were fronts to steal data and IP from users who are stupid enough to upload corporate and business stuff to them.

Anyway, there's vanishingly little I haven't been able to do over the years with ffmpeg or Imagemagick, their byzantine command line structures notwithstanding.

The website mentions that there are fake offline converters that push malware as well.