A comment on the YouTube video makes a good point that we already have a better word for the concept of dealing with multiple things at once: multitasking.

I don't think that's a good comment at all. In fact, it ignores fundamental traits that separate both concepts. For example, the concept of multitasking is tied to single-threaded task switching whereas concurrency has a much broader meaning, which covers multi threaded and multiprocess execution of many tasks that may or may not yield or be assigned to different cores, processors, or even nodes.

Meaning, concurrency has a much broader meaning that goes well beyond "doing many things at once". Such as parallelism and asynchronous programming.