A professional type setter is saying this, not Corsi.
No computer or pro type setter will vouch for this thing. None.
How about an expert on manual typewriters?
"Typography" is an ambiguous term. Most often it relates to the arrangement of type for printing, not to the study of typewriters and their typescripts. An "expert in typography" could be a forensic consultant, but might be -- more likely would be -- somebody who produced and knew much about printed, as opposed to typed documents.
Nowadays everybody wants to play CSI, but was Paul Irey really a forensic document analyst or FBI typewriter consultant or just a guy who worked with type for printing? Judging from his analysis I suspect he's the latter.
Irey does mention the IBM Selectric in his analyses, but that typewriter only came out a few days before Obama presumably was born and would not have been used. It doesn't look like Irey knows or cares much about manual typewriters and their quirks.
One thing noted in the blogs: Irey is working from that black and white (or black on gray) graphic. This is already a scan or copy of a copy and the letters are bound to be a bit coarser and less defined than they are in the black on green graphic (or in the original). Depending on the resolution of the various graphics involved what he comes up with is bound to be different from any "original" document.