He's right. I think this is an interesting area and set to grow in importance as clubs get more savvy about lashing out tens of millions on the next big player.
Technical skills deployed with intelligence are far more devastating than without. But it is not all about IQ - personality and character are equally important to effectiveness both in the immediate moment during games and also to sustaining form and careers.
The worlds top players have a blend of:
1)technical skill,
2)athleticism, 3)
high IQ and
4) the right personality traits.
MLT for example had 1,3,4 in abundance but perhaps less athletic by nature and slightly lazy, unambitious personality. This stopped him becoming a word-stage, world beater but allowed Saints to benefit for an entire career of his mesmeric technical genius.
Roy Keane had a fair amount of 1, a lot of 2 and 3 and, crucially, a ruthlessly psychopathic 4. Powerful mix that made him a leader and dynamo and successful at club level.
Maradona - had 1 massively, 2 a lot, and less of 3, and is a basket case re 4: hence his career trajectory.
The top clubs recognise these dimensions and do their homework for the most part not only on footballing skills but IQ and personality of players. Ferguson was good at this.
Luke Shaw - a bit dim by all accounts - this could limit his ceiling as a player ultimately.