Do you have empirical evidence of this claim or was it heard while sipping chai with mechanic or was it forwarded on whatsapp etc?
Havoline coolant (dexcool) is probably the most used coolant in the world right now as its long life and has almost negligible electrolysis issues. I have opened up engines with more than 400,000 kms that were cooled by dexcool and the castings of the engine looked fresh as the day it came from the factory.
The deposits you see on the thermostat housing are probably due to a leaking gasket or using the wrong kind of hose clamps, those perforated screw type "jubilee" clamps are straight up trash for modern cooling systems. Use the original spring clamp or buy higher tension smooth bore hose clamps like the gemi, torro and aba branded clamps you see on old Mercedes Benz and BMW cars.