> it's hard not to read this as a moral page turning on American culture.

Are unsupervised examinations common in the US? Or is this, in fact, simply one institution coming in to line with common US national and international practice?

This is not common in an in-person setting -- nearly "unheard of" outside of elite schools or particular faculty at particular programs. So it is the latter

It’s pretty common in WASP-y circles.