Ok, lets shift the focus away from the current flaw, obviously intended for a companion or grog who has spent all but the last few months in the wild, and on to a new flaw or flaws that might be allowable for a magus to take.
Some existing flaws might work:
This background could simply be a great explanation for having "Animal Ken", "Berserk", "Faerie Blood", "Famous" (the genius wolf), "Inofensive to Animals", "Improved Characteristics" (physical), "Skinchanger", "Ways of the (Land)", and/or "Wilderness Sense" in the Virtues.
As for flaws, it could be represented by "Ability Block" (language, charm, etc), "Afflicted Tongue", "Animal Companion", "Black Sheep" (if you were raised in the wild by sheep...no wait, how about if your family isn't thrilled about how you pee on the dinner table), "Compulsion" (to act wild), "Dark Secret" (What? The great Tempestus is simply a signified wolf?), "Delusion" (pack mentality), "Fury", "Hatred" (prey or predator), "Infamous", "Judged Unfairly", "Lycanthrope", "Magical Animal Companion", "Social Handicap", "Weak Parens" (to represent the difficulty your master had getting you to intergrate to the student/teacher dynamic).
Now, if you want a more specific flaw, and there's always room for more flaws, isn't there, you could look to "Sheltered Upbringing", "Faerie Upbringing", and "Feral Upbringing" to come up with something to represent a magus who, at least 15 years ago was feral. The problem with something like this, to my mind, is that if you were able to intergrate with your master and his covenant and pass your gauntlet to some extent you obviously aren't too feral now. And if your background doesn't limit you much, it doesn't seem like much of a flaw.
I think the restricted experience for the first five years of your life from "Feral Upbringing" still fits. "Faerie Upbringing" and "Sheltered Upbringing" are are both Minor Personality Flaws, "Sheltered" being the most applicable, and adding its limitation against taking certain skills during the rest of creation seems good, too. However, this is aimed at a Magus, so perhaps it should be a Hermetic Flaw. Now we have a flaw similar to several others, but still different.
Apprenticed From The Wild
As a child you were raised in the wilderness by animals or surviving on your own. In your first five years you gain 120 points which must be split between (Area) Lore, Animal Handling, Athletics, Awareness, Brawl, Hunt, Stealth, Survival, and Swim. You were likely found in the wild while still young, and having the gift, were trained, with some difficulty no doubt to be a Hermetic apprentice. As all your effort was directed to learing totally foreign matters such as vocal teaching methods you had no time to develop an understanding or the wider world. You are unable to function well in normal or Hermetic society, at least to begin with, and may not take Bargain, Charm, Etiquette, Folk Ken, Guile, Intrigue, or Leadership as beginning Abilities, but you may learn them in play. This flaw goes well with "Weak Parens", that flaw not reflecting the weakness of your Master, but the initial difficulty in training you. You must take a Latin Score of at least 3.
Hows that? It combines parts of two flaws, but doesn't limit a character's future growth to know and understand either society.