What is the name of the vocal technique used in these videos?
Technically speaking those are "falsetto" tones and not a "head voice".
Falsetto (from the Italian word for "false") describes the mechanism that occurs when the vocal folds temporarily "blow open" which produces a flute-like tone (as in the links you've mentioned).
This is different from "head voice"; which is a Falsetto that has been modified by the shape of the mouth to create more downward pressure on the air as it flows out, which in the end causes the note to resonate more like a chest tone.
"Just a small-town girl" (and most of the song's lyrics) are sung in classic "head voice".
Journey - Don't Stop Believing
Here's a YouTube video by Robert Lunte who sings a Falsetto tone immediately followed by a head tone (which he also calls "twang mode").
I believe they are jumping from their "chest" voice to "head" voice or normal voice to falsetto? Using falsetto to hit a high note but not have to belt it out so they can sing it lightly and also give it a slightly different timbre. Going into falsetto is a technique used a lot in pop music I think and other types of music. It is sort of like yodeling, although not as rigorous or technical as that, but similar in the way they just sort of pop into the falsetto for just one note. I guess I don't know if there is a specific name for that type of technique in this context though.
