I agree with all you have written, however I feel its important to reply to:

> for smaller projects with simple and more or less static UIs, and where the tests were all fundamentally scripted, there was almost no advantage to coding the tests later.

How many times in my career have I been asked to meaningfully design tests for basic static sites? Hardly ever.

Complex, multi-tenanted, many user-ed hydras with dynamic client side rendered content? All the time.

The scenario in which that Google presentation suggests it's most effective is the rarest ever, in my experience, especially if site is complex enough to have someone working on the team with browser automation coding experience/ability in the first place.