So just read both sites! That is what I do.
He may have picked the vmkfansite to talk to because they attempt to adhere to the vmk values...no discussing of personal information. The Disboards do not do that...you can see pictures of people, their locations, ages.
He may have picked that site because it was more established as a vmk info site before the disboards had a vmk section.
There are many vmk sites out there, he can't join them all.