This is one of those "weird" (in a good way) posts that could go well either here or in [email protected]. Randall Munroe typically researches the stuff well enough so his comics aren't just some empty joke.

Relevant tidbit: which gestures you're allowed to skip and how much is fairly language-dependent. Sometimes it changes even between closely related variety. English typically has a lot of wiggling room for that due to the stress-based timing, you're expected to reduce unstressed syllables. While Spanish for example isn't too prone for that (it does happen, mind you; just not as much. Except if you're Chilean.), with proficient speakers instead speaking faster.

Those simplifications often have their own names. For example, the ones shown in the comic are mostly adjacent assimilation, with a few deletions.

There's also a qualitative difference between the first two steps and the last one: the first two have been "encoded" into the language's morphology already, to the point that they're productive (cue to "tryna"), so they're a lot like the contractions nowadays. While the last one is mostly phonetic only in nature.