Point taken; here's the one from the 2024 Prius Prime owners' manual: Looks like they don't promise not to use engine braking in B, they just say they'll use it "or" strong (regen) braking. Of course they've just got plenty more battery to fill before they need to think about limiting it.
This whole thread, including OP's and RJ's cars, are not plug-in versions, so don't have the PHEV's EV-B mode. (Excepting a low-speed corner case.)