Toyota Red is not OAT coolant, it is IAT (Inorganic Acid Technology). It is similar to the old "green" coolant you refer to. Don't base what happened with GM engines and DEX-COOL with Toyota engines. I don't believe the head gasket failures in the late 90'-early 2000's were due to red coolant.

Your 2021 Toyota has PINK coolant which is OAT.

I've been driving Toyotas since 1974 , have always used the factory recommended coolant and have never had a bad head gasket.

My 2016 4R has pink coolant and I trust Toyota info saying that this is the best coolant for this engine. Use green if you want, it is your vehicle.