This is kind of an extreme case, to be fair it doesn't really disprove the statement which was about normal aftermarket car part markets.
Since this whole Tesla parts thing came up, I've always found it ironic that you can easily buy an entire powertrain based on the stereotypical half-century-old American V8 design and put it into a not-so-safe hot-rod, register it and drive it on the road (not that I'm saying that's a bad thing --- I'm a car enthusiast myself), but Tesla will refuse to sell you even minor cosmetic parts and quote "safety" as one of the reasons (and meanwhile, their misleading advertising for "autopilot" continues to generate deaths.)