As long as things are strong enough that is actually an advantage. As an offshore racing sailor, I've learned that weight is the enemy of performance and there is no point in making things stronger/heavier than they need to be, especially as this often has knock on deleterious effects on other parts of the platform. It is pretty easy to get in a vicious instead of virtuous spiral when making "upgrades". People immediately make the assumption that Toyota made its engineering choices to save cost, but while that is always a consideration, I'm sure the engineers were more concerned with performance and reliability while designing the platform.
The 300 Series is a Station Wagon Land Cruiser, while the 250 is a Light-Duty Land Cruiser two tools designed for different jobs. Comparing them is fundamentally flawed. The 300 should be compared to other Station Wagons, like the 200, not a light-duty Land Cruiser.At the end of the day, one’s a light-duty Land Cruiser, and the other is a Station Wagon. Seeing smaller or lighter components on the 250 shouldn’t be surprising it’s purpose-built for lighter use. it’s just engineered differently for its role as a Light Duty Land Cruiser.