I haven't seen the heads off a modern HM car with high fuel dilution, any issues with a ridge?I started trade school in 1971 and most of the stuff we got to work on was 10-15 years old, at less than 100K the cylinders usually had a deep ridge.
The oil was not very good and this sort of excessive wear was common. This was the era where products like MoS2, STP and others may have been of some benefit.