I just bought modern warfare 2019 on the current Steam sale and hopped on the game for the first time since the Halloween event when the SAW and TCM bundles were released long ago. I signed into my account and to my surprise, I still had the skin. I've been playing a lot of matches, and I haven't seen anyone using Billy or Leatherface. I always thought I wasted my money buying this bundle since it didn't transfer over to the current Warzone game and that's all I played at the time.