Decimation was way worse than reduction by a tenth. It was a punishment in the Roman army where the offending unit was divided into groups of 10 and each group had to draw straws. Whoever drew the short straw must be stoned or clubbed to death by the other 9.

If you threatened me with death if I didn't cut off my feet, I wouldn't consider that "reduction by 10%" even if mathematically it might be.