I would also think that it would be difficult to assess wether or not all of this exposure makes a difference because how can it accurately be measured? To make it even more complicated would be to try and study the best forms or styles of teaching such young children. Getting an actual measurement of what child learns or retains after being introduced to something would be near impossible. At such a young age children may understand much more than we realize. They just may not be able to communicate what they know yet.
I also think that children are very attuned to the emotional state of their parents. If a parents are stressed because they feel this unnecessary pressure to mold their child's brain, than their child will respond and begin "coping". As many studies have shown, there are long term negative effects to stressful environments in early childhood.