It’s a real interesting one this, part of my role involves oil analysis and Tribology generally. Oil degrades over time the Lexus will have had to input a ‘lifetime’ value into the calculations to determine whether they would need to replace. I suggest that have deemed it be be ‘good enough’ in reality.
Also worth noting that oils degrade over time, as well as mileage so must have attributed a length of time, along with mileage into their calcs.
I think it’s all a risk assessment by them to determine that the benefits of not doing it outweigh the tolerable risk of failure…