The writer is way off. The original Henry was indeed a rim fire but it was .44 caliber.
Okay I read the article more closely and the writer got it more or less right.
I have a Henry lever action that has a tube magazine (no side gate) but you have to pull out the plunger/spring to load the gun. It's "ok" for plinking and piddling, but is risky if you're just "topping off" the rounds already in the gun.
Your hand has to get dangerously close to the muzzle to load thusly.
He did say he was a newbie & still learning. :-)