The old school use of thermal isolators is to prevent boiling the fuel in the carburetor. (Not applicable here.)
The old school use of spacers is to increase plenum volume for better fuel distribution, and throttle response.
On a port injected engine you may see some effect on throttle response but everything else is moot.
Will a 65deg lower throttle body temp lower air temp? Logically, yes. How much? I would be surprised if it were more than one degree.
Note that the "analysis" was after 10min cool down. I don't care what the temp is after cool down, what is it when running under load? Also notice the before spacer throttle body temp was amazingly close to 180deg; coolant flow to the throttle body with a 180deg T-stat.