I've noticed some people start the game by triggering two cutscenes at the very start after gaining control of Jill, causing Barry to make a comment about her having cold feet.

What's the benefit to this? Does it affect enemy placement or something?

It's faster than the other option. If you do not do that, you'd have to exit the room with barry, trigger another scene with zombie there, come back to barry's room and trigger yet another scene.

So, if you do the cold feet start, you can skip going to Kenneth's hallway for the first time? Wow, that's interesting, thanks!

That's exactly it, no problem! I didn't know about that one, till I've watches some streamers as well .-.