Very interesting video.
At one point in the video, they say that the Krag did not continue with the rod bayonet used in the last Trapdoors, because the Krag was a "package design" imported from overseas. Yes, it's true that the Krag rifle itself was a Norwegian design. But the bayonet chosen for use with the Krag was based on a Swiss design. So U.S. Ordnance mixed and matched elements as desired. They could have used a rod bayonet on the Krag if they had wanted.
Note that the first model Krag adopted (the M1894) had a full-length cleaning rod under the barrel. Two years later, the full length rod was replaced by a jointed one carried in the buttstock. The original M1894's were recalled to the armory and updated to the M1896 specs, filling the rod channel with a wood plug, etc. Unaltered M1894's with the full length rod are today some of the "holy grails" of U.S.martial collecting. (I'm lucky enough to have one. I once considered selling it, but the dealer I offered it to turned me down. And I wasn't even asking all that much for it. Oh well. His loss was my gain.)