Is a SR2+ substituent really more electron-withdrawing than NH3+?

As the electronegativity of nitrogen and sulfur are around 3.04 and 2.58, respectively (according to the Pauling scale). So according to that, $\ce{NH3+}$ should pull the electrons more towards it than what $\ce{SR2+}$ should. This argument has been put forth by Jan in his answer to a similar question [here](https://chemistry.stackexchange.com/questions/65106).


However, my textbook (Organic Chemistry by Subrata Sengupta) states that the exact opposite is true. Who is correct here?


[![statement](https://i.stack.imgur.com/EAiiu.jpg)](https://i.stack.imgur.com/EAiiu.jpg)


