Yeah, the points you mention are what I remember what photographers really dig about JXL. Also higher bit depth is a big deal for some pro photographers.
I actually studied photography (technically contemporary art, but photography was my main medium) but chose to not pursue a career in it. You are correct, bit depth matters. It is unlikely 32 bits will ever be needed for RAW files though.
Specifically, it matters for source files and intermediate files.
With RAW files from the camera, the higher the bit depth of the analog-to-digital conversion (ADC) step, the less posterization this introduces on the signal. Theoretically at least, you're still limited by the sensor's dynamic range, and there are other subtleties involved, like light perception being logarithmic instead of linear, but RAW encodings being linear[0][1]. But in simple terms: paired with a sensor with high dynamic range and good ADC, a higher bit depth results in less noise and higher dynamic range. Which allows one to recover more fine detail from shadows and highlights. Which makes the camera more forgiving in normally difficult lighting scenes (low light and/or high contrast). So a higher bit depth can aid in giving photographers creative freedom when shooting, and more flexibility in editing their photos without loss of fidelity.
So yes, it is an important cog in the machine that is the whole processing pipeline.
Having said that, as I mentioned our eyes perceive light logarithmically. The dynamic range of the human eye is... complicated to determine, because it adjusts so quickly. At night it may go up to 20 stops, during the day 14 stops is likely to be the typical range[2]. So it's probably not a coincidence that digital cameras have "stalled" at using 14 bits for their RAW files, typically: the photographer likely wouldn't be able to see more contrast in the lights and shadows before taking a photo anyway!
