I've seen these tanks all over the south and north-east and all had the thread setup I described. The shut-off valve (if there) has the pipe threads. Not the tank. The ones I'm talking about are the same as in this ad.
Just because that is the only one you have seen; or it might even be the most common; does not mean that is the only one they make.
The tank will have a buttress thread. 6mm thread for the 2 inch size or 8 mm thread for the 3 inch size.
To this you can screw on many different valves. American 2 inch valves will most likely be NPT but if the tote came from Europe it will be a 2 inch buttress thread.
You can buy adapters that adapt 2 inch buttress to 2 inch NPT so you can use American pipe on it.
Then they have that crazy 3 inch china valve. It looks like NPT but is not the same. I find it easier to just replace the valve with one I can work with.