With PTO putting in a Strength of Field and a Tier system, aren't these the same function?

Ideally, you'd want a win in [world class race with all the top performers] to be worth more than a win in [local race where mid-tier pro beats up on the local field]. But both SOF and the tiers reflect the same thing.

They've made both a judgement based decision as to which ones are the top races (I have no issue with which ones, its their race and ranking system they can do what they want), but SOF measures the same thing - the big guns (presumably) show up for the top races (which have the most points in their Tier), and you'll get extra points on SOF for beating the big guns.