There was an article about curing in Smallholder Feb 2011 which might be the one you mean. it prompted a similar discussion in our house.
Having read it a few times what they seem to be saying is that if you use saltpetre and plan to sell your products the saltpetre must be in the correct ratio, which is impossible to do accurately by hand so it advised pre mixed cures.
Here's the exact wording to see if others have the same interpretation:
''If you are planning on curing anything that has to last over a couple of weeks, you should use curing salt. this is a mixture of ordinary salt and saltpetre. By law, if you are going to sell your products, you need the saltpetre in the correct ratio, which is impossible to do in the kitchen, the amount is so low you'd never actually get the stuff properly mixed. You can buy it, however , along with any number of pre- mixed cures for really professional results'' Paul Peacock Smallholder magazine