The 1.55x has never looked this good on previous iPhone models. The adjustable aperture of the 18 Pro seems to make a huge difference in the overall detail and IQ. It also carries through on the video side and makes focusing much simpler.
The 1.55x was always pretty dreamy wide open and is even moreso on the 18 Pro, since it has a faster lens.
I have never tested it seriously on any of my other cameras, because it won’t cover full frame (whereas the 1.33x seems to if you find the right lens). But I suspect the 1.55x would actually work great on a M43 or APSC sensor.
Here is another iPhone shot from this evening. There were a few raindrops on the lens, which created some interesting artifacts.