[68Hawk]

I'll only speak from my limited experience using a guillotine cutter through my batchelor course work nearly 20 years ago....(a printing industry batchelors in graphic design and interactive media).

Firstly, so many things affect the cut. The number of sheets you load, the paper itself (which can be denser/wetter than desired, or variable in the fibre quality etc.), the sharpness of the blade, the handler themsleves and their own abilities etc, the condition of the stock paper before you put it under the cutter (eg. you can bump edges when trying to shift large format sheets across a factory room), and many others.

So many on this site seem to want to make an argument based on the assumption of perfect conditions resulting in perfect results. Any variation and the X files music starts up.
Truly, the more amazing thing is what a great job these early printers did producing a product as approx. uniform as it ends up, considering high print number runs and the fact these were 'giveaways' with the product - NOT the scarce highly priced collectable we consider it today. Each sheet and card would not have been handled with the trembling hands of today's t206 crazies.

Regarding angle cuts on one side, as you cut and turn the paper for the next cut, it's certainly possible to not butt the card stock uniformly enough up against the holding edge (or bump it without noticing) and create an angle cut on one side.....I did it myself a time or two when rushing. You might also have a single sheet midway within the stack that isn't uniform and don't realize it until seperation.

Also, importanly, paper that perhaps wasn't dried correctly before printing will continue to dry over subsequent years. And not always uniformly. You can get shrinkage that will 'suck up' the edges and create an out of square sheet giving a distinct dog ear appearance.

And to dog ears, while I agree some are clear tell tales of later re-cutting, some are just the process of aging/worn/played with/pressed in card holding binders of the era. I own a number of tobacco cards with cricket themes that had been held in a binder that clamped over the 4 corners tightly resulting in a flattening and 'elongating lengthening' perspective to each corner.
You can do it yourself with some card stock (don't use a valuable trading card :-). Just press down and out a number of times on a corner and you can lengthen it. Now imagine paper stock that gets a little weakened with handling, and the effect is even easier to have occur, naturally.

Overall, the argument to me runs simply to what can I see and prove, and what will I conject based on my limited knowledge.
I can't prove God exists through an absence of widely accepted observable evidence. But I can show through fossil records that not all the animals and everything else was created over a 6 day period. Neither of those statements gets me any closer to a positive position of how the earth began, they just are what they are.
If I know Jim Morrison hated Sesame Street but came across his auto on a Sesame Street album......if all the indications I could measure suggested the auto was authentic I wouldn't deny that likelihood just because of a storyline that might suggest otherwise. I would have to trust that on that day, things were different and the signing happened contrary to what I might expect.

If SGC pored over the card, and I'm sure they did for hours and hours, then their opinion of what they saw on the edges and corners led them in all they know on the topic to conclusively say that the card wasn't hand cut. Now the hows and the wherefores of this card coming into existence and having the slightly less than perfect angles and such isn't a story they see need to mess with.....they're just telling you what they are willing to certify to.
They would have sweated over it, and I'm pretty comfortable knowing that.