I don't think the data supports this, yet. Religiously affiliated completed TFR is 2.2 while unaffiliated is 1.8. However, completed TFR means this is looking at those older than 60, so expect those numbers to drop in the future.
https://www.pewresearch.org/religion/2025/02/26/religion-fer...
From my observations, TFR is not much different between most people who describe themselves as religious and most people who describe themselves as non religious. However, the TFR is different for those who I would describe as the most religious, compared to the "casually" religious/non religious.
For example:
https://danielgordis.substack.com/p/israel-has-high-birth-ra...