i dunno why all this second guessing.
the OEM tires were literally created for this specific car by Toyo. 33" AT3 116H didn't exist prior to the GX550. there was no use case for a Toyo A/T tire rated for 130MPH (H), definitely not a low-rolling resistance one.
the top speed of the GX550 is 115MPH, so they had to make a tire that would satisfy both the car, the EPA and the offroad influencers / youtubers.
seems like many of us don't go 130MPH, don't care as much about the EPA, and focus on a solid reliable tire that matches our personal habits, I think it's an overall reasonable compromise that gets us a good enough tire until we figure out how we want to customize the car to personal taste.
even the Lux model tires are a compromise between the 20"/22" "for looks" versus ride quality, but I think that market segment is already very well established and lexus had a much easier time finding a Japanese tire in that category that keeps most folks happy.