these biscuits are made with "strong" flour, which has a high protein content, typically 10-12%. soft or short biscuits are generally made with low protein flour (7-9%). a low protein flour makes a dough with a much weaker gluten web.
...
| property | protein |
|---|
| soft flour % | 8.0 |
|---|
| medium flour % | 10.3 |
|---|
| strong flour % | 13.2 |
|---|