Yes I read the same article I expect, about the team getting the ingredients, including some really odd ones. Of course they also must bring some of their own, like Kate and Ian last season, who grew half the stuff they used. They submit their ingredients list for the first and last, and then get given the stuff for the technical - and sometimes have to figure out how even to use it as the recipe doesn't say, but they'll know that if they're given sugar, it's supposed to be in there somewhere!
I do worry about some of the contestants reading stuff about themselves online, and hope that they avoid social media as much as possible during the time that it's shown! I hope also that they know that we know they are not necessarily like that in person, and that it's heavily edited to produce a particular effect. It's almost like we all are commenting on the characters that the producers have created, rather than the people themselves - but I bet it is hard for them to really accept that.