Short slow cooking times?

I recently bought a new slow cooker recipe book as I work quite late and it would be nice to come home from work to food ready to eat. Most of the recipes sound amazing and I can't wait to try them out, however some of them MUCH lower cooking times then I am used to seeing in a slow cooker recipe. For example there are recipes for peri-peri rice in 45 minutes on high, Pollo Picante which uses butterflied chicken breast 1 hour 5 minutes on high or 2 hours 5 minutes on low, Harrissa Cod 2 hours on low, 1.4kg beef topside 2 hours on high or 3 hours 30 minutes on low. Most recipes I've seen and used previously would be at least 5-6 hours on low. Will the meat really be properly cooked all the way through with such a short slow cooking time? submitted by /u/BoopieJellyfish