Yes of course the studies were randomised, that is the entire point. If you use a group of hypochondriacs claiming it affects them then obviously the result is going to be tainted and scientifically invalid.
Not if youre trying to prove that it is hypochondria.
Because its double blind if theyre just making it up you'll see the same elevated claims in both groups.
Which disproves thier claims.
Iirc this was done on people complaining about radio waves affecting them.
Sat in a room with an antenna they where told was turned on or off those who claimed radio waves afgected them negatively reported the same level of negative effects when it was on or off