Exactly my point, at that time even, Corolla was running at "Flat" EQ from the head unit not "Flat" as per RTA.
You are basing your assumption only on one install. Which was untuned and also undamped. 2ndly RCAs makes a huge difference and so does speaker wires. There were only 500 rupees wali RCAs installed in corolla.
Access sounded different on PG and different on Zapco. Well thats more of a comparison between amps not speakers. Every amp has its own signature sound. Which then is tamed with the help of an eq.
There are man reasons for brightness or harshness in sound in a tuned setup too. Not talking about the untuned one where mere speaker level switch in the passive xover might not be set right or improper tweet placement. Even in a tuned setup the tweets might sound bright or harsh due to poor installation, reflections, bad TA and spill cause the tweet to be harsh.