I have a VERY pressured life. It makes me exhausted, occasionally frustrated, often curt and impatient, sometimes very unpleasant to be around. it also makes me incredibly productive, fulfilled, and content. I most certainly am happy under this kind of pressure.
BUT that doesn’t mean everyone is. Some people thrive on pressure and rise to the challenge. Others are buried under its weight; they could achieve the same heights under a more relaxed regimen.
SO, while it may not be unhealthy for you to learn 10-12 hours a day as a 12-13 year old (or 17-20 year old, for that matter), it may be very destructive for others. Chinuch l’naar al pi darcho. You are right, in thinking that some of this “softness” may be attributable to general social norms and standards where kids are under less pressure and so are unable to handle the pressure as well. But, the reality is that social norms are here, they do impact on how kids handle life, and we need to work with these realities rather than try to ignore them and expect kids to fall in line.