I am not so sure about scrubbing meaning, but seems to be that your issue is about the certainly to get it.......
To use SN instead N just can to be about money and it is a logical reason. Another reason is wrong surely.
There are N powders and N veterinary liquid.
The N liquid advantage is that you know what you have, 6,3 grms/100ml.............powders not, you will have to test it or take the risk.
About taste, what can I say you................it is known taste issues of N liquid, I do not know about powders.....
About suppliers, N vet liquid is reliable, there are a lot of people who have got it, myself for example. About N powders I am not so confident about people who say to have it, but it could be trustworthy.
About customs, there is not safe about that problem, If it seized.....bad luck!. That risk is inevitable.