It seems to stem from the idea that stagger is a hangover from the typewriter, in which it was required to make room for the mechanics, and that if we didn’t need to make them like that, we wouldn’t have.
Hence the keys should be lined up so your fingers just move up and down.
However I think this has 2 problems.
1) Most ortho keyboards have 5 columns for 4 fingers.
2) In stagger I use different fingers to strike the same letter dependent on what the preceding letter was, so that I almost never use the same finger twice in a row. You can’t do this in ortho if the 2 letters are in the same column, leading to more repeated strikes from the same finger.
Which I would expect is both slower and more straining.
But maybe my technique is weird, or haven’t given the ortho enough time.
(if you like ortho, good for you, not trying to spoil your fun, just musing)