No, ShackTac is playing Arma 3 with vanila sounds. Just ask Dslyecxi. No mods. For reference i will post another video where he explains some things like supersonic crack. Also i ma really confused how can anyone confused vanilla sound with modded do people even play Arma 3, do they know that sounds got updated after marksman DLC? Supersonic crack and subsonic sound of fly by bullet is in engine, using weapons that aren't part of vanilla content does not change vanilla sounds. Yes, they will add sound for those weapons that were added, but weapons don't determine the sound of stuff like supersonic crack, that is determined by something else which can be changed with sound mods but ShackTac isn't using one.
https://www.youtube.com/watch?v=tWjKx2wlgKs - watch the whole video