That third row looks like it will have 0 headroom

Third row in any vehicle not a giant SUV is a nightmare for any average sized adult.

And from the image in the video, it looks like the back row seats didn't even have headrests.

If it fits 4ft humans that would be plenty so long as there is somewhere else to fit a 6ft human

I had to do - 'Empty cache and hard reload' to get the updated page.

Model Y looks like a child of Model 3 and Model X.

I too had to nuke both tesla.com cookies and also "force.com" ones (a CRM by salesforce). Seems like it has aggressive caching. Incognito also resolves it.

Off topic: I wish pages would stop hijacking my scroll. It makes for a jerky/buggy experience that I hate.

Scrolljacking is always bad. I have come across about two instances where it was almost decent, but they still managed to be bad. This is not one of those; this is one of the usual lot that are just plain bad with no redeeming features. Completely unusable on my laptop with touch, and infuriating to scroll with the touchpad or keyboard. And disabling JavaScript isn’t an option because then the entire page is completely broken.

or just add some gubbins onto the url https://www.tesla.com/modely?a=1 works

Is that mcguffins? Like in the Pulp Fiction briefcase? :)