With G-SYNC, Reflex (and LLM Ultra) auto limits itself lower the higher the refresh rate is, so that's expected. At 240Hz, it limits to 224 FPS. It's just how it is. Ask Nvidia *shrugs.*
And to be clear here, Reflex has both an auto FPS limit for keeping the framerate within the G-SYNC range (the 171 you're seeing at 180Hz), and a dynamic FPS limit for whenever the GPU usage becomes maxed (at which point it caps slightly below the currently achievable average).
Again though, prioritizing render queue settings intended to reduce latency in GPU-bound scenarios for non-GPU-bound scenarios is a bit of a moot point. If you don't like what Reflex is doing (benign as what you're seeing is), and your system is not GPU-bound in the given game, you don't have to use it.
It continually perplexes me as to why such settings seem to be fixated on by so many.
Setting a manual FPS limit to keep G-SYNC in range AND your GPU usage from maxing is as good as you're going to get on the render queue and display latency front where a no-tear configuration is concerned.
Settings like LLM and Reflex are really only applicable (and intended) for situations where your system can't maintain a constant framerate and it begins to frequently fluctuate below your desired target.