The typical Lawn Grass is still bugged when using Path Tracer. Density is sparse and Path Tracer ignores height. This has been a known issue since early 2022 and unfortunately it was not addressed in the 2023 preview.
You can use a taller grass option and set the height to 0 as a work-around but it's still much taller than typical Lawn Grass and any other detailed grasses you do (dandelions, weeds, etc.) must be set to a taller height for visibility.
Is this on your radar to address?