It’s not only unacceptable, it is a clear violation of the Florida Building Code. Roofing systems are designed for installation according to their approval, and you will find no approval from any listed manufacturer stating they will warranty their product for that type of use. That being said, the code clearly states that all downspouts are to exit a minimum of 12" away from the structure sidewalls through an approved means of disposal. Ask the gutter contractor if he would terminate his downspout over a main panel or a/c compressor? No, common sense tells him that’s not a good idea. The key is, what is the acceptable form of disposal from a gutter system downspout, the code gives three options…underground piping, tail extensions, or splash blocks. Nothing on roofing systems being used as an approved location for the termination of downspout water.
***2010 Florida Building Code, Residential: R318.6 **Protection against decay and **termites. ***
*Condensate lines, irrigation/sprinkler system risers for spray heads, and roof downspouts shall discharge at least 1 foot (305 mm) away from the structure sidewall, whether by underground piping, tail extensions or splash blocks. Gutters with downspouts are required on all buildings with eaves of less than 6 inches (152 mm) horizontal projection except for gable end rakes or on a roof above another roof. *
I used the residential code as I was assuming it’s a SFR, the sizing of the gutters is listed in the Plumbing Code.