To be fair, many (all?) of these ships are burning https://en.wikipedia.org/wiki/Heavy_fuel_oil, which is not at all like petrol in that it requires preheating and atomisation to burn.
It still doesn't burn well unless it's in a fine mist. Even just a puddle of diesel is actually quite difficult to get burning on its own without some other material as a wick of sorts. https://youtu.be/7nL10C7FSbE Great practical demonstration of the different flammability characteristics of some common fuels.
For the tar that a container ship burns, it's not going to be very volatile. Coal also burns quite well, but unless it's powdered, good luck trying to ignite some with just a match.
I said pre-heated. No fuel burns in it's liquid form, it needs to be turned into a gas first. If you heat up diesel it'll light extremely easily as the vapor concentration is high.
So you learn no? I'm sure the way fuel was carried during World War 1 is not the way the US Military carries it now.
Special ships? That probably depends on the economics. If the Electric Car Industry makes it worth a shippers while - Someone will invest in a special purpose vehicle.
So now we are at the first stages of this - in time - if the industry succeeds - the money will come.