I see where you are coming from. Yes, those dough formulas do contain soda, but not in the context of just soda alone. The soda in the formulas that you have referenced is shown as a constituent part of a leavening system. That is why it is shown in brackets. As you will note, there are also leavening acids included with the soda, such as Monocalcium phosphate (MCP), sodium acid pyrophosphate (SAPP), there can also be glucano delta lactone (GDL), sodium aluminum phosphate (SAPP), and now that sodium reduction is all the rage, look for calcium acid pyrophosphate (CAPP) to become more popular.
Tom Lehmann/The Dough Doctor