The ones I missed were #27 and #28 in the video. 27 is a lady standing on the side when Tommy is giving you a tour of the hydroelectric plant. And 28 is the one with the banner on the school and Ellie comments on it.
If you got all of them, Idk what to tell ya. Maybe it was a glitch?
I don't think the chapter select will work. I noticed that when you choose chapter select, it doesn't save the progress from your beaten game, it just loads your progress from that point. Let's say you had 4 shiv doors unlocked when you met Henry and Sam, and you got 12 when you beat the game. If you choose chapter select to meet henry and sam, you'll only have 4 shiv doors unlocked again, instead of the 12. So I'm guessing if you do chapter select it won't work for conversations either..