So should I cut back on the octane booster or just see how the RN9Ys look after some road time?

No matter what the heat range numbers say for a particular plug ( or comparing different brands of plugs), the farther the porcelain and tip is from the plug housing, the hotter it is going to run.

I know of another guy in SO CA that worked in a knock lab also, he lead me to use the projected tip spark plugs in iron headed B and RB motors as well as all of the Mopar hemi motors for drag racing and street use
Same information, different conclusions
I had low compression(true 8.5 to 1) pump gas 350 Chevy boat motor that pinged, knocked, on regular pump gas with a Champion J12Y and quit knocking with a Champion J11Y
I worked in service stations a long time ago before they became gas stations only and I have seen many stock motors that needed the spark plugs heat range changed for the driver
Around town only grandma drive differently than there hot rodder grand kids did
Colder is always safer than a tiny bit to hot when it comes to gasoline and different driving conditions and fuel used

You had the same experience that a lot of racers and hot rodders have, they don't hear it until the motor quits or starts smoking
I learned to look at the plugs frequently until I knew the tune up was safe
On my stock 415 HP M.W. on the old 100+ octane high lead pump fuel in 1971 to 1973, it liked the stock J11Y, not the J10y or the hotter J12Y spark plugs. I could hear the difference in idling right away, I could see the differences in on the plugs with one full WOT blast down the street
As far as heat on the plug tip the center porclyn determines what the tip temperature will be, retracted or projected
More porclyn around the center electrode less heat transfer

Same piston exposed to detonation. BTW, never heard it until the damage was done.

Not apples to apples in a power adder situation and I've been using projected tips forever w/zreo issues as long as the carb/timing are where they need to be.............

True. Can't remember for sure, but with the boost I was running the static CR figured out to be around 17 -18:1. Projected tip plugs don't live there.

Plug electrode heat build up transfers through the porcelain to the plug main body. The farther it is from the main body, the less heat transfer there will be and the hotter the electrode will run. What I was always taught.

Smokey Yunick invented the projected tip plug--it has been std equip for 40-50 years now?? They are supposed to idle cleaner and better
I have been a hot rod nut and engine guy all my life --I have never had a better plug or better plug company than NGK--quality is unsurpassed--tech line answers phone on first rings and if you give correct info--all ya need is correct compression ratio--fuel type--and the proper thread engagement stuff like always They will put you ON THE MONEY first time if you give correct info Then you order off Ebay with free shipping and no sales tax and get the best for less--I tell this tale again and again but folks fight it and always have other opinions---
Yes Autolite race plugs and Champion race series are good plugs but tech is almost non-existent and price is just stupid compared to NGK on Egay
Just try call NGK tech which you can Google
These are the best quality plugs available Japanese made --superior quality--Amazing tech support--and best price of all the quality units available
Quit fighting City Hall and try em will ya???

I'd like to see some ACTUAL results from using different brands of the same heat range plugs. I would guess that there wouldn't be much difference to measure. I would have to say yes to the original question. At some point sharp edges and projectile tips will retain more heat in the combustion chamber. Common sense.