expectationvsreality

It's common in America when you want a quick rise or to increase moisture in the end product. Conversely, some recipes encourage proofing the dough in the fridge. This reduces yeast activity while retaining amylase activity, resulting in more sugar (maltose usually in this case) in the bread. In general, the best practice is to use the starches in the bread as the sugar for the yeast to develop complex flavor.

In the end bread is not an exact science and there's lots of variables to play around with to get what you want. It's just at 10 percent sugar you've certainly gone beyond that.