Read it he didnt say the turret he said the hull gun..
Even if it was a Sherman with the flame thrower using the main gun (US Army used mix, main turret flame thrower and hull gun flame thrower), it would still have a couple of hundred yard range that it could stand off at and still hit buildings in the town.
There is a book called Cutthroats, its the story of a Sherman tank driver in the Pacific and his tank was "shanghaied" and fitted with the hull gun flame thrower while another tank in their platoon was outfitted with the main gun flame thrower that had a farther range than the hull gun flame thrower. The tanker, Robert C. Dick, hated the flame thrower and was glad they got rid of it when the pressure failed and the napalm barely exited the barrel and ended up catching their tank (#60) on fire but they were glad they were still able to use the main gun, unlike their buddies in tank 59.
ack-ack