I am pretty sure that is 300Mbps shared. And you rarely get that even in real world best case scenario. And much worst if you live in City and High Rise Buildings with High Density population.
DOCSIS 3.1 brings OFDM as well as up to 10 DL /1 UL Gbps. At that sort of speed, as well other added reliability features finally makes Cable a decent Alternative. Speaking from experience in EU and Asia Area. No idea if it is the same in US.