I think you misunderstood my poor explanation of the reaction. The overall rxn is:
2 NaHCO3 + GBL -(heat)-> NaGHB + H20 + CO2
The intermediate and stronger base, Na2CO3, is formed decomposition of baking soda in hot water. The bicarbonate ion formed by dissolving NaHCO3 is not stable in hot water... 2 HCO3- -> CO32- + H20 + CO2. And, it is the sodium carbonate that goes on to react with the GHB that is formed by the base promoted hydrolysis of GBL with water.
Btw, my reasoning to why using baking soda, is at the very least, a comparable method to using NaOH, is in the post right above the question. (some people...) Another factor is price and availability, NaHCO3 is often cheaper and is available at your supermarket or corner store, unlike ACS grade NaOH.