Correct and very perceptive, sir. They were special TRW domed pistons designed with a 'quench dome' on the spark plug side that came up very close to the stock chamber wall on that side, and a slot in the dome for the flame front to pass through. One of the claims made was that the quench air 'squirt' would push the flame front out faster and help the combustion process. The designed CR was over 11, but I ground out the other side of the chambers some to get the CR down to the low 10's for pump gas, and CC'd them all. I dunno how good the quench was, but the engine ran without detonation on pump gas, and the DCR had to be up in the mid 8 range with that cam. (60 degree ABDC intake closure).
The Clevelands and boss motors were also helped with a stock 1.73 rocker ratio; you could get gobs of lift with low duration. That was one of the first thing I learned here about the SBM: the 1.5 stock rocker ratio drives you to use longer durations and thus higher RPM's and higher stall TC's and rear gears. All just due to a seemingly minor design difference.
It was all a pretty good training ground for a 21 year old aspiring gearhead.... the engine is still in the garage.... temptations abound....And its the pattern for what we are doing with my son's 340: We're going with 1.6 rockers just to get some of that higher lift-to-duration ratio back....as well as working for 10:1 SCR and quench.