Here's a quick question: If you have a monster PC, does that monster get this +4, +4, +2, +2, +0, –2 ability score bonus a normal monster with PC class levels would get?
Not really: Those modifiers are basically the PF variant for the elite array. They're there so you can have a stronger-than-normal braele fighter, a smarter-than-usual sprite wizard, or a more-charismatic-than-the-average owlbear bard.
Usually, when you let someone play a monster character, he instead rolls for his stats, or uses the purchase method - or whatever you're using for ability score generation - and applies the monster's ability modifiers (equal to their listed ability score -10, or -11 if it's an uneven value)