Location: Minneapolis/St. Paul, Minnesota - Latitude 45.057 Longitude -93.074
Rewards Points: 2,066
10 x 20 slab
I does not seem to male sense, so I would talk to your city code/inspection people to see if that applies to a slab. They may have a requirement for a thickend edge if you are placing some lightly loaded posts on the slab. Most cities will have design/installation suggestions to make everything easier and clear.
There are model codes(IBC, IRC, etc.) that states and municpalities adopt. Since they are just minimum standards (the worst you can do and not be put in jail for), but the locality has the authority for tighter requirements, usually based on local conditions (soil, weather, wind, seismic, snow etc.).
If it is a suppliers requirement, you will have absolutely no guarantees if it is not installed to their standards.