The "most poisonous spider" bit is not necessarily true. It is true that it's mouth is too small to penetrate human skin. As there have been no reported incidents of bites from them, there has been relatively little testing. 

 Because of that, the whole "most poisonous spider" story remains unconfirmed. Some of the "Daddy Longlegs" which exist don't even have poison glands (harvestmen, for example, don't have poison glands).