I listened to the presenter tell us Alan Kay "kind of soured on it [inheritance]" 13:45

The source doesn't say that.

I listened to the presenter tell us "… look at what they were actually talking about when they were talking about Smalltalk in the times before they had chance to reflect and say that it [inheritance] didn't work". 14:10

The source doesn't say that.

I listened to the presenter tell us "… literally representing in the hierarchy what our domain model is. … They have a Path class and from that Path class they have different shapes derived from it." 14:46

Chapter 20 "Smalltalk-80: The Language and its Implementation" describes how Graphics was implemented in the Smalltalk-80 system —

"Class Path is the basic superclass of the graphic display objects that represent trajectories. Instances of Path refer to an OrderedCollection and to a Form. The elements of the collection are Points. … LinearFit and Spline are defined as subclasses of Path. … Class Curve is a subclass of Path. It represents a hyperbola that is tangent to lines … Straight lines can be defined in terms of Paths. A Line is a Path specified by two points." page 400

As they say in the Preface — "Subclasses support the ability to factor the system in order to avoid repetitions of the same concepts in many different places. … subclassing as a means to inherit and to refine existing capability."

I listened to the rest of part one.