I agree with the notion that the word Salat here does not mean ‘namaz’!
The two words “Salat” and “Zakat” have different, yet consistent, meanings in 9:5 and in 9:11. The word "Salat" in these verses is used in its narrow sense of "establishing peace" because in its broader sense it means "establishing the Divine system" while the Divine system aims at establishing global peace. Similarly, the word “Zakat” in these verses means “purification of self/having no evil thoughts”. Thus, the verses 9:5,11, in essence, mean that “if you repent, return to peace with a purified hearts, Allah is forgiving and you will be considered our brothers….but if you return to war, then know that…..”