When i was a youngster steam locos were still in use, but being replaced by diesel.
I had no idea there were ever as many flavors of steam engines until i saw your video 1 link.
Live and learn
One of the video's mentioned a project underway to build a new steam engine.
Will it ever really happen or is it vaporware ?
Who knows, but if someone does it, MAYBE a new Steam Loco speed record is possible.