You heard right. Absolutely no baffles in the tank, so you either had to empty or fill up after every fire. No power steering or servo brakes either, they were a nightmare to drive and kin hard work! Initially I was sent out after only 3 days' learning to drive the damn thing, on just a normal driving licence. Then one got rolled in Manchester and two squaddies were killed unfortunately, so the powers-that-be decided we all had to have a minimum of HGV3 to drive them thereafter. As a result, came off duty one morning, drove from Oxford back to Aldershot, went straight off and did my test, passed, drove straight back to Oxford and went on duty again that evening. Elfin Safety would probably put a stop to that kind of goings-on these days...
I never rolled one, but did smack a plod car up the jacksie (did some serious damage too!) when misjudging its size while attending a fire down some narrow street of terraced houses. Got a summons for careless driving for that, but was let off after the strike was finished, under a government diktat that gave an amnesty for most offences committed by squaddies driving the GGs, on the grounds that it had been a national emergency. Result!