I like to keep things simple - like a ball on the end of a string. The longer the string, the faster you can get the ball moving. True, the longer the string the more effort it takes to get it going, but once it gets going, watch out. I think my comment about "hand speed" may be the wrong terminology for this discussion, but borrowing from the article, longer arm segments - assuming you have the strength to get them moving - will translate into more velocity. Taller kids generally have longer arm segments. Assuming the taller kid does not have more muscle, then they perhaps have lower arm speed, but the longer arm segments allows the kid to throw as fast or faster.
What is missing from Kyle's article that struck me was a possible third component to arm speed - that being generated from the shoulders (think throwing something solely by turning you shoulders and letting your arm swing freely - no elbow extension or rotation). Especially for pitchers that throw with a lower positon (less overheard and more with arm extended out from plane of shoulder allowing shoulders to increase whip action).
Glad I don't make my living handing out pitching advice or calculating re-entry points for NASA (saw Hidden Figures this weekend - pretty good movie).