Section 1507.2.9 of the Florida Building Code 6th edition 2017 states that:
“Flashing for asphalt shingles shall comply with this section or RAS 111. Flashing shall be applied in accordance with this section, the asphalt shingle manufacturer’s printed instructions or the RAS 111” Section 1507.2.9.1 says the same thing only references “base flashing” in particular.
The manufacturer’s printed instructions are what ARMA recommends, ie…step flashing. ARMA’s installation manual under “flashing”, states that ”roof planes that butt against vertical walls at the end of shingle courses are best protected by metal “flashing shingles” placed over the end of each course. The method is called “step flashing”. GAF even shows this same method in their application manual.
So it is not mandated by code in Florida, it is one of three allowed sources of guidance on how to do it, and the only one recommended by the most recognized source in the asphalt shingle world. So if you also believe it’s the best way, you are free to do so under Florida code.