Guaranteed contracts are worth cash. They can fire him tomorrow, but they have to pay him for 5 years. You don’t give someone a 5 year contract if you plan on having a short window to prove himself.
Who said they were planning on having a short window to prove himself? What you plan on doing and what actually happens have little to do with each other. Stephen Ross doesn't strike me as a man of patience. I think there will have to be some signs of progress by year 2 to guarantee he stays for year 3. Hell if the right coach drops into his lap, I can see Ross eating Flores contract in less then 2 years. Flores will have the money, but he won't have a job.