It seems the disparity has grown in recent years imo, but I haven't heard many others note this. For instance 2014 and 2015 STEP I I found doable (scraped a 1 sitting 2015, think I could have done better with less crap exam strategy/time management, high 1/low S when doing 2014 as a mock), whereas I looked at the II papers for each year and, while admittedly not trying forever, couldn't get a single full solution. But STEP II papers from longer ago seem a lot more approachable.