I check friends’ Snapchat stories from time to time, and Snapchat suggests public stories on the same page. I think Snapchat has the same sort of singular data point on me that “this account is likely a straight man”, because most of what they show me are sports clips, woman influencers in revealing clothing, and right-wing influencers talking about culture war stuff. I never view any of that sort of stuff, but it still shows up any time I try to check my friend’s stories. I guess I view public stories so infrequently that they just give me a default generic man feed.

You are correct. He used a VPN for several US locations in the video. He then compared what content was shown in different regions of the US to see if everyone sees the same thing or if the content is radically different depending on where you are.