Coming back to this, i recently saw that this is a typical artefact for a too wide extrusion width compared to the nozzle width, coupled with maybe a bit too high of a temperature.
This may show in the benchy especially because of the drawn out overhangs.
Yes the trigger height for the IR sensor against transparent PrintBite can be rather variable, probably because of the texture inside it. The new black PrintBite is better. However, on a delta printer it's better to use a nozzle contact probe if you can, because any sensor that is offset from the nozzle will be affected by effector tilt.