“Police-grade” flash bangs are regulated by the BATFE and are a felony for unlicensed sale, possession or use. So whatever devices the antifa had they were not this class of device.
see for example.
http://www.att-tactical.com/att_sales_bangs.html
The flash bangs may have been stolen police equipment. In pics from Berkeley they look like the real deal. What is needed is to collect the remains and check for serial numbers.